You can re-attempt your assessment
Students should review their answers before submitting. When you click Save & review you'll see a Summary of attempt screen showing which questions have been answered.
If you click on Submit all and finish before you're ready, you'll need to re-attempt the assessment by returning to the assessment overview page and clicking Re-attempt quiz (don't worry, all of your previous responses will be there).
Finish off the questions you missed or upload any files you need to and resubmit the assessment.