My personal basic tools for learning:

• man bash. That's the documentation for everything. It's very careful and serious though, so sometimes you need...
• Search in internet if you think your particular question is very "repeatable". Stackoverflow used to be good, but now they're all "AI AI AI by the way have you heard about AI?". So I'm not recommending it anymore. For "advanced bash" there are pages that go over those "advanced topics", too!
• Run shellcheck to read your code and give suggestions/warnings. It's a great tool for learning, too, besides the primary goal of reviewing code to be production-ready.
• Sometimes, with extreme care, ask an LLM to review your code or give siggestions. It tends to hallucinate a lot, makes up wrong and unexisting stuff, but sometimes it's useful, too. Especially at finding bugs. Again, it can be useful, but use with care. Oh, and it can actually be great at explaining, too. Throw it some syntax/code and it'll explain wtf is going on. This part is very reliable and good.

At my current level of experience I need mostly man bash, and occasionally all of the rest. Before I used a lot of stackoverflow and simply thinking of what I even want.