So, I joined a hardware company as a software developer few months back. I'm working on a c++ code base with thousands of files and no idea what the code is supposed to do.

I got one overview of what the product is supposed to do, which contains mostly electrical engineering jargon that I have no clue about.

Now my manager wants me fix a bug in this code. I have no clue what the expected behaviour is and no documentation whatsoever, and literally no one in the entire country who understands the code.