Got to ask a question, how much do I need to learn in order to be able to code adequately?
Well that's a pretty broad topic, but at the lower end you don't really need to know much to make cool things happen! Like right now we have
this event on r/RoguelikeDev which just started a couple weeks ago (I also mentioned it
here on the forums, by the way)
Some people start the event with zero programming knowledge and end up with a roguelike they can then expand on and build into their own thing, where for the first couple months you're doing it alongside others and can often get help if you have any questions. There are a crazy number of tutorials and other resources online these days, plus having a supportive community is helpful.
Some really big games have started with that tutorial, although not everyone has to use the tutorial, either--others use it as a general guideline while working with some other language or library/framework of their choice.
And how does contributing to code work? Does someone contribute by taking all the code, changing it, and giving it back?
With regard to opens source (or team) projects, the code lives online somewhere like GitHub (or some other type of source control), and you can make modifications and merge them with the main code base that others are also working with. You can read an introduction
here.
