You can read published games’ code pretty easily (as long as you have access to the part of the game you’re looking at normally – for example, I can’t view code for Heroes Rise beyond the first couple scenes because I haven’t bought the game). There’s a thread explaining how here:
I’ve learned a lot just by diving in and learning how to do stuff as I need it. Coding tutorials tend to be way more interesting and easier to follow if you’ve got a specific goal in mind. Learning about concepts in isolation isn’t particularly memorable, but suddenly finding a new way to solve a problem is very satisfying