There is a graphic that has helped me in a variety of sistuation. It may help you, too. I take paper, and draw a big light bulb. It’s on the page with “rays” in th form of lines coming out of it.
I write the subject in the middle of the light bulb, and use the rays to write topics and thoughts. I add rays where I need them and event sub-sets of rays.
Then take the ideas and organize them.
You can do the same with each new subject you’re learning and/or writing about.