@mitu Just a quick update. I compared the .bin/.cue files on my pi to the database. It turned out, that half of the .bin file was corrupted so I just had to put them again on my Pi0. And now MGS runs pretty well. Thanks for the help! :)

Its not hard. You just have to hold R2 at the title screen, and the link word will go away. Making it possible to play split screen. Have 2 controllers setup. Hold R2 with player 1 controller at title screen. Link will disappear. I just did it.

@schuhbidu https://github.com/RetroPie/RetroPie-Setup/wiki/Playstation-1#enhanced-graphics