UPDATE: Kodi does the same thing at first, but after about a minute or so, it just starts working for no reason

@CrazyPharaoh Sorry, I have the same problem whit my Waveshare 5 inch

Quick update:

Managed to make it run a lot smoother using those parameters:

dtoverlay=waveshare35a:rotate=270,swapxy=1,speed=27000000,fps=60.

The higher the speed, the better it displays, but anything above 27000000 f'd up the colors badly for me.
Definitely playable for anyone wanting to use this screen, but it still drops some frames, mainly during cinematics and stuff. Personally, Gonna try out a 5" HDMI screen, don't wanna compromise on the gaming experience too much.

Thanks it worked.
The emulator was not centered in the picture so i had to change the resolution under RETROARCH -> Settings -> Video and width and height. it was 12807someting and i put the resolution of the screen 480320