Thank you for your help and sorry for the delayed reply.
I think I found the problem because gnome shell also freezed when I try to Carmageddon: Max Damage. It was a faulty installation of Nvidia GL Libs.
Hey guy's!
I'm using the Ubuntu Linux 18.04 LTS, OpenJDK 8 and the vanilla FTB Launcher. Sometimes after fresh boot up and starting the launcher the Gnome shell freezes. I dunno why.
Can anyone help?
I attached the logs for some debugging.