Understand the basics: buffers, windows and tabs
If you are like me, chances are you used Neovim for a period of time without knowing the basics. The notion of buffers windows and tabs in Vim is quite different from other IDEs/code editors. I suggest you read through this and this Stackoverflow answer to get some understanding of this matter.
I'm almost ashamed to say this but I've never used or properly understood tabs in (n)vim. I think it's finally time to properly learn about them :) Thanks!