You can retake the quizzes an unlimited number of times. The purpose of the quizzes is not to trip you up to fail, but rather to act as a yardstick to gauge your progress. Even if you decide to retake the program, you are able to retake the quizzes in each course.
If you’re having difficulty with a certain concept, don’t hesitate to ask a question in the Q&A tab for that lesson or course. The guys enjoy providing additional context and welcome any and all questions.