What more can i do to truely understand the codebase? How things work, why they work, etc. For a product i developed fully, i know every inch of it, how it works, every single detail, now i want to work on different codebases and I am realizing is harder to make a change because if i make a change in x then y and z need to be updated/changed right and i wouldnt know so how could i contribute if i dont know how things work.