You can see the help forum and post your question there. It is an open discussion forum where participants can also answer each other's questions and the course concerned teachers can also provide guidance related to the usage of the platform or concepts in general.

You can complete the course in an orderly fashion by watching every video, filling out all the green circles that indicate some kind of activity, and submitting your quizzes. Start by going through each chapter thoroughly and pay attention to the empty circle which you have to do them to make them green.