can I remove some how SP from skills?? (I m 28lvl namakien)

Yes. Go to your class trainer to reset them. However, after you reach Lv.31, you won't be able to reset them anymore without using a Skill Reset Book, which can only be obtained through the Cash Shop or from other players, at high prices.

and where is class trainer? ^-^

Everywhere... For example, here.

thanks =D

Does it matter if u chose any class trainer npc to reset skill. Is there any different?

No that doesnt matter