There's lots of it now, but yeah its kinda painful.
https://duckduckgo.com/?q=reverse+engineering+with+ghidra&ia=web
When it disassembles its like very log level C code (or java code, in that case)
Part of understanding it is putting it back together.
What I'd start with doing is creating a few small C programs that do simple things.
Create a file, read a file, print text, pull text from a website (http, not https).
Compile them, then disassemble them and see what they look like.
After that start looking at harder things like compression, ssl, complex data structures, and so on.