LaTeX book
There are a lot of books and other different sources which allow you to learn LaTeX. However, most of them don't allow you to read them for free or show only a part of a whole book.
In this book (https://github.com/AnMnv/eBook) the author tries to reveal how you can find necessary pieces of LaTeX code looking only at already done work.
Yes, of course, you can try to google your task and find similar results, but sometimes it’s harder than you think. However, using the book, if you look at it briefly once, you will be able to find a needle solution next time easily, because every example is very noticeable. Moreover, there are a plenty amount of unique and necessary parts of code that can be very useful daily.