Lua is a 100% must, C++ not so much unless you're planning on making
your own source edits.
I've written a small book to help new people learn Lua here if you'd like to read:
Guide to scripting with Lua (https://otland.net/threads/guide-to-scripting-with-lua.265958/)
Knowledge of XML should be a given as well for script registration / other configurations (not a programming language, but you need to be familiar with the syntax).
If you're planning on creating your own website as well, yes, all of those web development languages you mentioned, you need to be comfortable with. Otherwise, you can just use one of the premade AACs.
If you're set on trying to learn C++, I learned some of what I know from learncpp.com, but a major chunk of my knowledge on C++ now comes from me messing around with TFS sources and having 200 tabs open with stackoverflow to learn and understand why what i'm writing in that moment is/isn't working.
Best thing I can tell you is to practice while you're learning, try to understand
why and
how code works, especially if someone gives you a code snippet (or even a full script). Also try to practice what you're learning, even if you're just remaking someone else's code or editing some small part of it. You're still applying what knowledge you just learned and putting it into practice, and helps you retain that knowledge for future use.