I used to play WoW and I can try to translate.
Quote: "i booggied about 50 naxxramas-runs"
Naxxramas is probably a dungeon or raid (like a big dungeon that can have teams of more people), probably something I never did on WoW. I quit soon after I started doing raids.
Quote: "runs with my cat at the endboss or dragon with stupid pull-actions (well, not 50 but an enormous number )"
He played the game with his cat, fluffles, I hear fluffles is your type Benjamin, you never know what'll happen if you play your cards right.
I am going to assume he's referring to a class in the game called 'Druid', who have the ability to transform into different animal forms - your cat form is great for dealing damage, whilst your bear form is good for taking it. Endboss - the boss at the end of the raid/dungeon and I'm guessing he's a dragon.
Quote: "there was an official court case of my guild on the server, even hordes-people where invited. i was judged to convert to bear (tank) for a minimum of 3 months. well, what should i say, i laid the naxx-bosses in my first tank-run. "
And this one seems bizarre even for my experience of the game. I didn't know any people had in-game court cases on players. I'm going to guess this was an 'RP' server (or roleplaying, where people tend to play the game in character). Basically, this poor druid was humiliated in front of lots of people and was pushed to only play as a druid in bear form.
Yes, I do feel ashamed that I know those things.
Though talking of druids, when I used to do dungeons, on quite a few occassions I found people came in as a tank, but used their cat form, whenever I was a healer (on my low level Shaman), that was really annoying as it becomes impossible to keep people alive and generally, the enemy would come for me sooner or later when it's the job of the tank to make sure the enemies are attacking them and nobody else. Heck, I used to be a Death Knight Blood Tank and it wasn't exactly rocket surgery, sure people have to learn as you can't automatically be aweosme (and it helps to listen to what people are saying), but I think some people just want to watch the world (of warcraft) burn.
On the note of tanking, this is a fail on behalf of my dungeon group (and a win on my behalf). I was playing a hunter, got disconnected, when I reconnected every except me and the healer had rushed ahead (to a point where they couldn't get back to us), so the tank had basically rushed off without a healer. Then the healer aggro'd, so I decided to intervene and tanked the enemies on my hunter (which aren't supposed to tank of course), with the guy healing me, neither of us died and we successfully killed all the aggro. Then everybody starts calling me a 'noob' because I was trying to Hunter tank. Right, the fact I tanked successfully on my hunter, saved the healer and the actual tank was miles away makes me a noob.

Good old WoW.