I'm just not sure about those slops - i know they suposed to be simple, but looks kind of weird when player stand on the bottom sprite overlapse withe the horizontal platform and when he's on top one of his legs is on the platform and the other one is in the air
Yeah, it's just a very basic example. This is just a beginner's tutorial, something to give you an idea of how something works. This method for slopes could be expanded to make smoother slopes where the overlap doesn't occur, or you could tweak your animations so they look right, etc. Or you could go with a different method entirely.
But if I showed that sort of stuff it would take forever. And after all, it's a tutorial, not a full, polished game. It's a starting point for new users, and hopefully will give them the knowledge they need to expand these methods into what they want to do, not just copy/paste the code into their own game.