Edit the group question's details.

After you've created the Group question, you can edit it.
To edit the group question, go to Contents > Courses > Selected course > Select the quiz and then click the "Continue" option.
When you arrive here, select the More option.
Next, select the Question Groups option from the dropdown menu.
The list of question groups is provided below. Select the desired one.
If you want to add new questions to the group, select the Add Question button.
If you want to change the group details, click the Edit Group detail option.
You can now change the group's title, instruction, and difficulty level here.
When you've finished editing the group's details, click the Save button.

You can edit and add questions to your group questions.