I started to get recently a crash at the startup of Minecraft, I don't really know what causes it. https://pastebin.com/MexvU5Lw

You should do some more testing and then report back if the issue persists. Try removing any coremods, including optifine, and post the crash if it still happens. If it doesn't, add the mods back until it does.

This really shouldn't happen on a client. Either the mod file is corrupted or another (probably core-) mod messes it up. Please (re)download the latest version of the mod and try again.

I redownload it and don't get more the crash. It was a really strange crash, I hadn't any ideas what caused it. Anyway thanks for the help guys.

No problem. I guess the file somehow got currupted.