When i want to do stuff with the Mod in Minecraft its crashing.

Error message:
The game crashed whilst unexpected error
Error: java.lang.ClassCastException: Cannot cast java.lang.Double to com.teamwizardry.librarianlib.features.math.Vec2d
Exit-Code: -1

You're either using mismatched Wizardry/LibrarianLib versions, or you got your mod files from a place other than CurseForge. Both have the same fix - go to CurseForge and make sure you get the latest of both.