Why are most people too complicated and confusing? It stresses me out😩

They really aren't. Most people are super basic. You can read one book and understand the vast majority of them. It's really just nature. The only complicated part is understanding all the constantly changing factors that make them different from you. And even that can be broken down to simpler forms.
This person was beaten, that person was raped. The simple factor there is abuse.
Like with all things, learn the basics, and the rest will follow with ease