I am having trouble full understanding set theory, I have read many different articles, but I still don't understand most of it.
Is their a good way to thoroughly learn set theory? Maybe some books?
I think the best book on Set Theory for music is Joseph Straus’ textbook Introduction to Post-Tonal Theory. It is not a simple text, I use it in an undergraduate class, but it’s closer to a graduate level. That’s especially true of earlier editions, but the newest edition (a rare example of a new edition that isn’t just a barely updated version of previous editions) is quite a bit more approachable. Like most textbooks, it is shockingly expensive for its relative size however.
If you have any Tonal Theory textbooks from prior theory studies, there’s a decent chance that some of the later chapters will give you a decent introduction. I know that both Kostka/Payne and Clendinning/Marvin do. It’s worth checking if that gives you enough of an introduction, especially if you already own the text.
In other words, this is one of those topics that actually is worth starting with a textbook, not by trying to dive into articles which will tend to assume prior knowledge. It’s still enough of a niche, academic area that people haven’t written many approachable or cheap introductions (that are good) yet. I would not recommend starting with Allen Forte’s book Structure of Atonal Music as it is more difficult and contains a number of oddities that have been ironed out over the years. It is an amazing book and well worth reading eventually, but it would be less helpful as an introduction.