Game crashes, error log included :)

It looks like some game files are missing in your installation (at least the interface.jar file is not present, which caused this particular error) You could try to verify the integrity of your game cache: https://support.steampowered.c…=2037-QEUH-3335&l=english
If that does not work, maybe it helps to delete the game and reinstall it (but make a backup of the Worlds folder)

Glad to hear that!