I write the problematic parts on a whiteboard (well, the wall because I have whiteboard paint and it makes note taking a fun activity actually) and after a chap

I write the problematic parts on a whiteboard (well, the wall because I have whiteboard paint and it makes note taking a fun activity actually) and after a chapter I read my notes again together with the book hoping now it's clear. If necessary, I will jot down my notes into a Google doc. I found it exceptionally helpful when learning frameworks to write a blog post even if noone will ever read it on how I figured out things, it basically cements what I learned. One of the best univ classes I went to allowed a single handwritten page "cheat sheet" at the exam -- in reality, the only one cheated was yourself because if you actually put in the work of condensing the semester into a single sheet then you usually learned the material during the process... sneaky.