Hello, gmmoon0824. I see you had some difficulties while studying. I could have just ignored it, but I appreciate you leaving such valuable feedback. I tend to explain the parts I think are important or seem a bit difficult multiple times, but I think I should try to reduce the repetition and explain them in a more concise way. Also, if you have any difficulties while studying, please feel free to use the question board. I and the supporters will help you all the way!