Unable to play minecraft whatsoever

So the "crash"txt is what happens when I try to log into single player, but when I log into multiplayer, the following text appears:

"java.lang.NullPointerException: group"

I really dont know what im supposed to do because im a 15 y/o white boy with no god damn idea what im supposed to be doing. So I would like it if you guys helped.

I'd love to change the "Priority Level" to Major since i can't do anything and it's blocks me from playing whatsoever. Please help.