My math course has 20, 2 hour online lectures on each chapter and I got frustrated with doing them and started to solve the problems on my own after downloading the lecture sheets. I study the the basics from my textbook and the relevant lectures. I also just watch the bits I'm confused about and make sure my process and answers are correct. My friends at college actually watch the full lectures. I don't want to learn any less than them, is my method of studying harmful, effective or neutral compared to them?