diff --git a/main/exercise/Annotation.php b/main/exercise/Annotation.php
index 43b46f0b70..6ec65f99c3 100644
--- a/main/exercise/Annotation.php
+++ b/main/exercise/Annotation.php
@@ -11,8 +11,8 @@
  */
 class Annotation extends Question
 {
-    public static $typePicture = 'annotation.png';
-    public static $explanationLangVar = 'Annotation';
+    public $typePicture = 'annotation.png';
+    public $explanationLangVar = 'Annotation';
 
     /**
      * Annotation constructor.
diff --git a/main/exercise/Draggable.php b/main/exercise/Draggable.php
index 3916aea886..94e1792295 100644
--- a/main/exercise/Draggable.php
+++ b/main/exercise/Draggable.php
@@ -8,8 +8,8 @@
  */
 class Draggable extends Question
 {
-    public static $typePicture = 'ordering.png';
-    public static $explanationLangVar = 'Draggable';
+    public $typePicture = 'ordering.png';
+    public $explanationLangVar = 'Draggable';
 
     /**
      * Class constructor.
diff --git a/main/exercise/MatchingDraggable.php b/main/exercise/MatchingDraggable.php
index 666c1802e0..06d2fed3a0 100644
--- a/main/exercise/MatchingDraggable.php
+++ b/main/exercise/MatchingDraggable.php
@@ -8,8 +8,8 @@
  */
 class MatchingDraggable extends Question
 {
-    public static $typePicture = 'matchingdrag.png';
-    public static $explanationLangVar = 'MatchingDraggable';
+    public $typePicture = 'matchingdrag.png';
+    public $explanationLangVar = 'MatchingDraggable';
 
     /**
      * Class constructor.
diff --git a/main/exercise/MultipleAnswerTrueFalseDegreeCertainty.php b/main/exercise/MultipleAnswerTrueFalseDegreeCertainty.php
index 6aaedda2d7..37a1853125 100644
--- a/main/exercise/MultipleAnswerTrueFalseDegreeCertainty.php
+++ b/main/exercise/MultipleAnswerTrueFalseDegreeCertainty.php
@@ -18,8 +18,8 @@ class MultipleAnswerTrueFalseDegreeCertainty extends Question
     const LEVEL_LIGHTRED = 4;
     const LEVEL_DARKRED = 5;
 
-    public static $typePicture = 'mccert.png';
-    public static $explanationLangVar = 'MultipleAnswerTrueFalseDegreeCertainty';
+    public $typePicture = 'mccert.png';
+    public $explanationLangVar = 'MultipleAnswerTrueFalseDegreeCertainty';
     public $optionsTitle;
     public $options;
 
diff --git a/main/exercise/ReadingComprehension.php b/main/exercise/ReadingComprehension.php
index e093709650..f04d799f1d 100755
--- a/main/exercise/ReadingComprehension.php
+++ b/main/exercise/ReadingComprehension.php
@@ -11,8 +11,8 @@
  */
 class ReadingComprehension extends UniqueAnswer
 {
-    public static $typePicture = 'reading-comprehension.png';
-    public static $explanationLangVar = 'ReadingComprehension';
+    public $typePicture = 'reading-comprehension.png';
+    public $explanationLangVar = 'ReadingComprehension';
 
     /**
      * Defines the different speeds of scrolling for the reading window,
diff --git a/main/exercise/UniqueAnswerImage.php b/main/exercise/UniqueAnswerImage.php
index 333be370c3..bfd3ee02fc 100644
--- a/main/exercise/UniqueAnswerImage.php
+++ b/main/exercise/UniqueAnswerImage.php
@@ -10,8 +10,8 @@ use ChamiloSession as Session;
  */
 class UniqueAnswerImage extends UniqueAnswer
 {
-    public static $typePicture = 'uaimg.png';
-    public static $explanationLangVar = 'UniqueAnswerImage';
+    public $typePicture = 'uaimg.png';
+    public $explanationLangVar = 'UniqueAnswerImage';
 
     /**
      * UniqueAnswerImage constructor.
diff --git a/main/exercise/calculated_answer.class.php b/main/exercise/calculated_answer.class.php
index 94ea1e7420..f7ef9f8e72 100644
--- a/main/exercise/calculated_answer.class.php
+++ b/main/exercise/calculated_answer.class.php
@@ -13,8 +13,8 @@ use Webit\Util\EvalMath\EvalMath;
  */
 class CalculatedAnswer extends Question
 {
-    public static $typePicture = 'calculated_answer.png';
-    public static $explanationLangVar = 'CalculatedAnswer';
+    public $typePicture = 'calculated_answer.png';
+    public $explanationLangVar = 'CalculatedAnswer';
 
     /**
      * Constructor.
diff --git a/main/exercise/fill_blanks.class.php b/main/exercise/fill_blanks.class.php
index c280028f39..aa9b246ed2 100755
--- a/main/exercise/fill_blanks.class.php
+++ b/main/exercise/fill_blanks.class.php
@@ -15,8 +15,8 @@ class FillBlanks extends Question
     const FILL_THE_BLANK_MENU = 1;
     const FILL_THE_BLANK_SEVERAL_ANSWER = 2;
 
-    public static $typePicture = 'fill_in_blanks.png';
-    public static $explanationLangVar = 'FillBlanks';
+    public $typePicture = 'fill_in_blanks.png';
+    public $explanationLangVar = 'FillBlanks';
 
     /**
      * Constructor.
diff --git a/main/exercise/freeanswer.class.php b/main/exercise/freeanswer.class.php
index 4306d196b6..567564920a 100755
--- a/main/exercise/freeanswer.class.php
+++ b/main/exercise/freeanswer.class.php
@@ -12,8 +12,8 @@
  */
 class FreeAnswer extends Question
 {
-    public static $typePicture = 'open_answer.png';
-    public static $explanationLangVar = 'FreeAnswer';
+    public $typePicture = 'open_answer.png';
+    public $explanationLangVar = 'FreeAnswer';
 
     /**
      * Constructor.
diff --git a/main/exercise/global_multiple_answer.class.php b/main/exercise/global_multiple_answer.class.php
index 0aff5c7fb6..cfb8df0bd9 100755
--- a/main/exercise/global_multiple_answer.class.php
+++ b/main/exercise/global_multiple_answer.class.php
@@ -8,8 +8,8 @@ use ChamiloSession as Session;
  */
 class GlobalMultipleAnswer extends Question
 {
-    public static $typePicture = 'mcmagl.png';
-    public static $explanationLangVar = 'GlobalMultipleAnswer';
+    public $typePicture = 'mcmagl.png';
+    public $explanationLangVar = 'GlobalMultipleAnswer';
 
     /**
      * GlobalMultipleAnswer constructor.
diff --git a/main/exercise/hotspot.class.php b/main/exercise/hotspot.class.php
index 93a80fbdfd..eb52d84536 100755
--- a/main/exercise/hotspot.class.php
+++ b/main/exercise/hotspot.class.php
@@ -14,8 +14,8 @@
  */
 class HotSpot extends Question
 {
-    public static $typePicture = 'hotspot.png';
-    public static $explanationLangVar = 'HotSpot';
+    public $typePicture = 'hotspot.png';
+    public $explanationLangVar = 'HotSpot';
 
     /**
      * HotSpot constructor.
diff --git a/main/exercise/matching.class.php b/main/exercise/matching.class.php
index cb7c6753c5..8156cdc303 100755
--- a/main/exercise/matching.class.php
+++ b/main/exercise/matching.class.php
@@ -15,8 +15,8 @@
  */
 class Matching extends Question
 {
-    public static $typePicture = 'matching.png';
-    public static $explanationLangVar = 'Matching';
+    public $typePicture = 'matching.png';
+    public $explanationLangVar = 'Matching';
 
     /**
      * Constructor.
diff --git a/main/exercise/multiple_answer.class.php b/main/exercise/multiple_answer.class.php
index 98233616e4..fe034ed3d7 100755
--- a/main/exercise/multiple_answer.class.php
+++ b/main/exercise/multiple_answer.class.php
@@ -15,8 +15,8 @@ use ChamiloSession as Session;
  */
 class MultipleAnswer extends Question
 {
-    public static $typePicture = 'mcma.png';
-    public static $explanationLangVar = 'MultipleSelect';
+    public $typePicture = 'mcma.png';
+    public $explanationLangVar = 'MultipleSelect';
 
     /**
      * Constructor.
diff --git a/main/exercise/multiple_answer_combination.class.php b/main/exercise/multiple_answer_combination.class.php
index 6be050cd62..ff476fb572 100755
--- a/main/exercise/multiple_answer_combination.class.php
+++ b/main/exercise/multiple_answer_combination.class.php
@@ -16,8 +16,8 @@ use ChamiloSession as Session;
  */
 class MultipleAnswerCombination extends Question
 {
-    public static $typePicture = 'mcmac.png';
-    public static $explanationLangVar = 'MultipleSelectCombination';
+    public $typePicture = 'mcmac.png';
+    public $explanationLangVar = 'MultipleSelectCombination';
 
     /**
      * Constructor.
diff --git a/main/exercise/multiple_answer_combination_true_false.class.php b/main/exercise/multiple_answer_combination_true_false.class.php
index dd5c6313f1..8afaa439ee 100755
--- a/main/exercise/multiple_answer_combination_true_false.class.php
+++ b/main/exercise/multiple_answer_combination_true_false.class.php
@@ -13,8 +13,8 @@
  */
 class MultipleAnswerCombinationTrueFalse extends MultipleAnswerCombination
 {
-    public static $typePicture = 'mcmaco.png';
-    public static $explanationLangVar = 'MultipleAnswerCombinationTrueFalse';
+    public $typePicture = 'mcmaco.png';
+    public $explanationLangVar = 'MultipleAnswerCombinationTrueFalse';
     public $options;
 
     /**
diff --git a/main/exercise/multiple_answer_true_false.class.php b/main/exercise/multiple_answer_true_false.class.php
index 43bbe1cd70..28fea63f5e 100755
--- a/main/exercise/multiple_answer_true_false.class.php
+++ b/main/exercise/multiple_answer_true_false.class.php
@@ -14,8 +14,8 @@ use ChamiloSession as Session;
  */
 class MultipleAnswerTrueFalse extends Question
 {
-    public static $typePicture = 'mcmao.png';
-    public static $explanationLangVar = 'MultipleAnswerTrueFalse';
+    public $typePicture = 'mcmao.png';
+    public $explanationLangVar = 'MultipleAnswerTrueFalse';
     public $options;
 
     /**
diff --git a/main/exercise/oral_expression.class.php b/main/exercise/oral_expression.class.php
index d9216fcf19..ef1ef8b673 100755
--- a/main/exercise/oral_expression.class.php
+++ b/main/exercise/oral_expression.class.php
@@ -12,8 +12,8 @@
  */
 class OralExpression extends Question
 {
-    public static $typePicture = 'audio_question.png';
-    public static $explanationLangVar = 'OralExpression';
+    public $typePicture = 'audio_question.png';
+    public $explanationLangVar = 'OralExpression';
     public $available_extensions = ['wav', 'ogg'];
     private $sessionId;
     private $userId;
diff --git a/main/exercise/question.class.php b/main/exercise/question.class.php
index df71c67831..a7833d0273 100755
--- a/main/exercise/question.class.php
+++ b/main/exercise/question.class.php
@@ -34,8 +34,8 @@ abstract class Question
     public $isContent;
     public $course;
     public $feedback;
-    public static $typePicture = 'new_question.png';
-    public static $explanationLangVar = '';
+    public $typePicture = 'new_question.png';
+    public $explanationLangVar = '';
     public $question_table_class = 'table table-striped';
     public $questionTypeWithFeedback;
     public $extra;
diff --git a/main/exercise/unique_answer.class.php b/main/exercise/unique_answer.class.php
index 6d633bb3dd..50660bcd9d 100755
--- a/main/exercise/unique_answer.class.php
+++ b/main/exercise/unique_answer.class.php
@@ -18,8 +18,8 @@ use ChamiloSession as Session;
  */
 class UniqueAnswer extends Question
 {
-    public static $typePicture = 'mcua.png';
-    public static $explanationLangVar = 'UniqueSelect';
+    public $typePicture = 'mcua.png';
+    public $explanationLangVar = 'UniqueSelect';
 
     /**
      * Constructor.
@@ -37,6 +37,7 @@ class UniqueAnswer extends Question
     public function createAnswersForm($form)
     {
         // Getting the exercise list
+        /** @var Exercise $obj_ex */
         $obj_ex = Session::read('objExercise');
 
         $editor_config = [
@@ -50,13 +51,6 @@ class UniqueAnswer extends Question
         $nb_answers = isset($_POST['nb_answers']) ? (int) $_POST['nb_answers'] : 4;
         $nb_answers += (isset($_POST['lessAnswers']) ? -1 : (isset($_POST['moreAnswers']) ? 1 : 0));
 
-        /*
-          Types of Feedback
-          $feedback_option[0]=get_lang('Feedback');
-          $feedback_option[1]=get_lang('DirectFeedback');
-          $feedback_option[2]=get_lang('NoFeedback');
-         */
-
         $feedback_title = '';
         switch ($obj_ex->getFeedbackType()) {
             case EXERCISE_FEEDBACK_TYPE_DIRECT:
@@ -99,8 +93,8 @@ class UniqueAnswer extends Question
         }
         $form->addElement('hidden', 'nb_answers');
 
-        //Feedback SELECT
-        $question_list = $obj_ex->selectQuestionList();
+        $obj_ex->setQuestionList(true);
+        $question_list = $obj_ex->getQuestionList();
         $select_question = [];
         $select_question[0] = get_lang('SelectTargetQuestion');
         if (is_array($question_list)) {
diff --git a/main/exercise/unique_answer_no_option.class.php b/main/exercise/unique_answer_no_option.class.php
index eb839f54c1..2681782034 100755
--- a/main/exercise/unique_answer_no_option.class.php
+++ b/main/exercise/unique_answer_no_option.class.php
@@ -15,8 +15,8 @@ use ChamiloSession as Session;
  */
 class UniqueAnswerNoOption extends Question
 {
-    public static $typePicture = 'mcuao.png';
-    public static $explanationLangVar = 'UniqueAnswerNoOption';
+    public $typePicture = 'mcuao.png';
+    public $explanationLangVar = 'UniqueAnswerNoOption';
 
     /**
      * Constructor.
diff --git a/main/inc/lib/sortable_table.class.php b/main/inc/lib/sortable_table.class.php
index a6bb85a671..6bf82a4001 100755
--- a/main/inc/lib/sortable_table.class.php
+++ b/main/inc/lib/sortable_table.class.php
@@ -132,7 +132,7 @@ class SortableTable extends HTML_Table
             $table_id = $table_name.uniqid('table', true);
         }
         if (isset($parameters) && empty($parameters)) {
-            $parameters = ['class' => 'table data_table', 'id' => $table_id];
+            $parameters = ['class' => 'table table-bordered table-striped', 'id' => $table_id];
         }
 
         $this->table_id = $table_id;
@@ -717,7 +717,7 @@ class SortableTable extends HTML_Table
         foreach ($param as $key => &$value) {
             $result[] = '<input type="hidden" name="'.$key.'" value="'.$value.'"/>';
         }
-        $result[] = '<select class="custom-select" name="'.$this->param_prefix.'per_page" onchange="javascript: this.form.submit();">';
+        $result[] = '<select style="width: auto;" class="form-control" name="'.$this->param_prefix.'per_page" onchange="javascript: this.form.submit();">';
         $list = [10, 20, 50, 100, 500, 1000];
 
         $rowList = api_get_configuration_value('table_row_list');
diff --git a/src/CoreBundle/Controller/Admin/SettingsController.php b/src/CoreBundle/Controller/Admin/SettingsController.php
index 1d32f9054f..bb39ea455f 100644
--- a/src/CoreBundle/Controller/Admin/SettingsController.php
+++ b/src/CoreBundle/Controller/Admin/SettingsController.php
@@ -178,10 +178,6 @@ class SettingsController extends SyliusSettingsController
             if (!empty($keywordFromGet)) {
                 return $this->redirect($request->headers->get('referer'));
             }
-
-            /*if ($request->headers->has('referer')) {
-                return $this->redirect($request->headers->get('referer'));
-            }*/
         }
         $schemas = $manager->getSchemas();
 
diff --git a/src/CoreBundle/Entity/ExtraField.php b/src/CoreBundle/Entity/ExtraField.php
index c03e38fc68..e51fccc296 100644
--- a/src/CoreBundle/Entity/ExtraField.php
+++ b/src/CoreBundle/Entity/ExtraField.php
@@ -32,6 +32,7 @@ class ExtraField // extends BaseAttribute
     public const TERMS_AND_CONDITION_TYPE = 14;
     public const FORUM_CATEGORY_TYPE = 15;
     public const FORUM_POST_TYPE = 16;
+    public const EXERCISE_FIELD_TYPE = 17;
 
     /**
      * @var int