If at least one learner has attempted a quiz, note that you will not be able to add or delete questions – you will only be able to make some corrections to quiz text. To update the quiz with substantial changes you will need to make a copy of the course and quiz and update the copy. Attempting to update a live course with substantial changes to functionality of assessed activities is not advisable or helpful to learners who may already have completed the original version, especially if the quiz counts towards course completion.