Unfortunately, once a quiz has been submitted it cannot be resumed.  One option for future quizzes could be the Build on last attempt option for New Quizzes.  In Settings under Allow multiple attempts you can select Enable build on last attempt. This should allow students to retake the quiz after submitting and only have to answer the questions they incorrectly answered in the previous attempts.

Release Screencast: 2023-09-16 New Quizzes Build on Last Attempt