Everybody learns differently, and there’s a lot of people who learn languages through advent of code. AoC can have some problems that could take literal years to solve with a naive solution, so just keep in mind you can cancel a slow function with C-g and you don’t need to reboot emacs entirely.

The other thing to keep in mind is that this would help you learn elisp (and general lisp syntax), but won’t teach you as much about the functionality you can do with emacs. It’s still a good place to start though, since you’ll need to know elisp to customize emacs.

Lastly I would recommend looking into Structural Editing a bit, here’s a decent article that covers the basics in vanilla emacs. This is by no means a requirement for writing elisp, but using the sexp commands makes working with all the parentheses infinitely easier.

Good luck!