Thank you two for your answers, I guess I have something to read now.
How many of these games did you finish?
I have made clones of Tetris, Snake, Minesweeper and a basic side scrolling shooter.
I mean a polished, playable game that could have been dropped into an arcade in the 80s and got people to play it
They all are playable, but they don't look very nice, because I'm no artist
With this new project, I want to work with some people, who are.
If you find that every time you change something something else breaks, or you're just randomly changing stuff guessing at the problem
No, that's fortunately not the problem. I have a very clean coding style, where every class just does its own job and when I change something, it usually just affects the class itself.
I just would like some basic ideas on how "professional" programmers structure their classes, maybe just a class diagram of a bigger game could do it, but I haven't found a good one yet.