I am about to start my third semester in CS B.sC and I feel like I've gotten better with C++ to learn any high-level library (like Qt and such) quickly, same with other programming languages, I can't code in Swift yet but if you tell me you have to be be able to build a prototype of an app with it by the end of next month I will be able to.

But I feel like all of that is just one skill, I have no idea about anything that isn't very abstracted away by languages/libraries, if I read any source code that isn't just calling functions with descriptive names I don't event attempt to read further. I want to be able to (for example) understand system libraries, be able to read linux kernel and at least be able to modify a bit of it myself, understand how building works internally, how to be able to contribute to large libraries without failing to even build them correctly.

Ive been watching a video about the xz backdoor on linux and it made me really intrigued to learn how that kind of stuff works on such low-level and be able to understand the code myself.

How do I start? I don't really know where to go.