A question note when study this complex coding. Really hope some experienced one gives me some learning suggetions

Hi, All. Here is a peice of coding I am learning. It is difficult as I have no ability to write only can read. I am trying my best to make every point clear while because there are many combinations I meet the first time, therefore, I would like to post my doubts here. Maybe I can get help from ur experienced guys. I upload the code here.
Please feel free to give me some suggestions (if not waste much time for you) on how to learn efficiently, many thanks in advance.
20201031 triangular random.gh (47.2 KB)

are you chinese? may be you can learn it in qq group

Yes, Chinese.
May I know the number of qq?