Me and my brother made a local server on his computer, a pretty good computer, he can run probably all games with high quality with no freezing or crash.
But when we play, both of our computer are awfully slow, even with the lowest quality (Tiny, fast, fog to the max, ...), the games not even fun to play in this conditions. My computer is bad but when he play alone, it's still slow.

So if any of you have an idea of what could be the problem, ideas of solutions, ways to faster it, ... Or if it's normal and that there's nothing to do, tell me because if I'm loosing my time... Well! Hope you can help.