There are enty of books you can read. If you’re really interested in learning I suggest you may start learning how to write bash.

For the rest I really would say, that just try doing stuff. Try to set up a docker, or other stuff. Also you can go to already solved Problems and try to understand what the problem was and what they did to solve it.

Also: Just start trying to support people. Google(or any other Search Engine of your liking) is very useful for this. Even if you just find out what exactly the problem is, that helps.