Hello, sorry I am not german, but it is an easy fix....
Open your skills file in skill editor, look at Weapon Type box, what this box is for is what weapon can use the skill, for NS its all -1 in both Type 1 and Type 2 boxes so the skill is meant to be used with "any" weapon, if you are an admin you can go NS learn skills change your class to whatever, you can still use NS skills... to fix this simple put "15" in either Type 1 or Type 2 box, which will link the skill with NS weapon which's ID is 15..
here is the screen shot, you can look at my Weapon Type box, type 1 is = 15 which is ID of NS weapon....
[Only registered and activated users can see links. Click Here To Register...]