What is a good way to understand geometry proofs?
- Read the theorem.
- Try to prove it yourself.
- Read its proof made by somebody else.
- Go to the next theorem, start from step (1).
If a novice, skip the item (2) for the first 10 theorems.
It is important to study geometry in logical order, from basic concepts and simple theorems to more complicated, where each subsequent topic is based on what has been proven before.
Good textbook (I mean, a really good textbook, not a set of bits of knowledge unrelated to each other, like in encyclopedia) is your best source.