Besides some of the very, very obvious (don’t copy/paste 100 lines of code, make it a function! Write comments for your future self who has forgotten this codebase 3 years from now!), I’m not sure how to write clean, efficient code that follows good practices.
In other words, I’m always privating my repos because I’m not sure if I’m doing some horrible beginner inefficiency/bad practice where I should be embarrassed for having written it, let alone for letting other people see it. Aside from https://refactoring.guru, where should I be learning and what should I be learning?
In my opinion, this article is extremely valuable: https://lexi-lambda.github.io/blog/2019/11/05/parse-don-t-validate/
You will not get through it without at least a Haskell cheatsheet, but the concepts it shows can (and should) be applied in any programming language, even if some are definitely more capable for this.
This might be a bit advanced, but indeed a very good article.