Leveling - bugged ? o0

No, it's not, it shows 6$.

It's probably still on the exploited/no-CV list since at some point it accidentally got a 99% discount, meaning pretty much everyone started hoarding copies.

http://www.sgcv.tk/sent/milan9123
It says 6$

No it says

Tropico 4 Collector's Bundle (1 Copy) (6$ Total)

This was not an explanation why you are level 1 (this is answered above), it's a hint that you should activate the copy of "Serious Sam HD: The First Encounter" you won on your account cause you seem to have forgotten to do that...