sorry i could not find title for this question and thats why sending it in mobile category:

1 my first question is how to remove sent sms?
2 how can i know if my account is hacked or someone other is using my account?

you can not delete sent items they are delete automatically on daily basis.
to check you account is hacked keep reviewing your login counter and last login time on profile page.

assalam o alaikum..
jumma tul wida sub musalmaanoon ko mubarak ho ..
ya allah humaray tutay putay rozay or nimazay or jin ebadat ka
humein salika nahe un ko apni bargah me kabool o maqbool farmana
or humein maaf farmana beshak tu bohat ghafooro raheem hai ...?
ameeeen summa ameeen .