What's the fastest way to learn how to modify the game engine through code?

Hi, What’s the fastest way one can learn how to code for the game engine / UPBGE (eevee preferably) to code in one’s own tools? I want to help the devs but I don’t know any thing related to coding engines except for the usual game engine coding. I plan on making mods or tools necessary for myself and then releasing them to everyone for them to add it into the engine, maybe as an addon? Any directions, hints, links, resources are appreciated .

So right now you can use bpy to create addons just like for blender and they can be included in upbge pretty easy.

Also look at how to build blender, then you will have the tools you need to edit the source.

Building upbge is pretty easy now

Just check it out and do make update