Read code! Pick some code that is widely used and just read it. You can try to figure out how some particular feature works. How does the Linux kernel load an ELF binary? There is a definite answer to this question and the answer is in the git repository. How does musl implement printf and how is it different from GNU libc? Maybe these don't interest you, but there is a lot of code out there. How does nasm represent instructions? What opcodes are used by GNU Emacs, how are they different from the ones in Guile? How does zlib or libjpeg work? So many questions, just pick something that you wondered about and go find out how it works. Having seen many examples of real things that work, you will remember them when you run into similar problems in your own work.