The tree diagram is quite easy to draw, from big to small.

Generally speaking, books are written in order and summarized in the order of books.

The teacher may have painted in class, right? Something like that

The tree diagram is mainly to look at it every day, to sort out ideas and not to use knowledge points to solve problems by mistake.

As for the accumulated experience, there is no other way except to do the problem. Science depends on solving problems. Do more problems and you will have experience. I suggest you buy more extracurricular exercises and do more, and you will improve.