u/DowngradedAshes

So Ive been installing mods to boost my FPS (performizer+ and it's mods that come with it) and it worked fine and stuff but for some reason I cannot play single player, only multiplayer servers that are available on the multiplayer tab, I cannot add servers too. If I try to load my world it will say this on the picture. I've tried restarting and redownloading, even redownloading Minecraft didn't work with just one mod and what comes with it. I really need help I suck at hive due to it still being laggy (I'm aiming for very very high FPS).