I am level 55 but cant use all Weapon´s?!

Hey guys,

I am fresh in old kult C.o.D 4 , level today with HighXP server get the Maxium level (like 55??)

but wanna buy the P90 but cant use it?! why??

see picture : https://i.imgur.com/xTAL281.png

my level : https://i.imgur.com/FemLo2r.png

idk :
last time I play with other nicknames and yet play with the profilname in game… lol

on the server , enter !rank where it works