Do I have to watch videos for postgraduate mathematics?
It depends on your foundation and self-discipline If you have a good foundation and no weak subjects, you can study by yourself. If you have good self-discipline, you can follow online courses. If you have two weak subjects, and your self-discipline is average, it is suggested that you report to face-to-face classes, let the teacher supervise the whole process, and be admitted to graduate school in one year.