I have a question that I hope I will be able to explain clearly...

I was thinking earlier: Most of my mathematical knowledge is like a branching "tree", in the sense that: You need algebra to understand calculus, and you need arithmetic to understand algebra. Also, you need caulcus to understand statistics. Similarly, you need algebra to understand matrix/linear algebra (but you don't necessarily need calculus for that), and you need matrix algebra to understand dynamical systems theory.

My point is probably clear.

Now I want to develop my knowledge and skills of mathematics further, and for that reason, I'm wondering what the "tree of knowledge" looks like for mathematics.

For example, if I want to learn group theory (which I do), then what would I have to learn first?

I know this is a kind of weird and general question, but: Is there some kind of website/book that gives an overview of all mathematical knowledge in a casual way?

The reason I'm asking this, is that right now, I don't have a clear picture at all of what we know about mathematics, and what I would need to learn first in order to learn about mathematical theory X or Y.

I'm not sure if my question is clear, so if itisn't, I'll be glad to clarify.

Thanks!