If you quiz contains items that cannot be graded automagically, you will have to grade those items manually.
If your quiz contains a mixture of auto-graded and manually graded items, learners will not receive any feedback until you have completed the manual grading.
Click the title of the quiz.
You can change the number of attempts shown at the top of the page. Be careful, though, fewer attempts per page means you lose less if something goes sideways.
You can review the grades in Grader Report.