My code is a mess

[Kiryu]

Hey, as the title suggests, I have a problem that often holds me back from continuing my projects, and that is my code!

Before I continue, the most important class in my current gamemaking project, a cubeworld clone.

Header: https://hastebin.com/ogodomococ.cpp
Source: https://hastebin.com/bomuqihoho.cpp

I think I'm not the only one thinking that this class is one big mess, and I want to get to know why. I've rewritten it many times, but still. What exactly it does is not that important, I just think its not very easly readable...

Anyone knows something that I tend to do wrong? Maybe some literature in that topic?

Thanks in advance! :)

PS: https://github.com/Kiryu144/Root/tree/master/source