I'm 16 and agnostic but almost everyone i know from family to friends are Christian. How do i deal with it?

Stop going to church if they are dragging you there. Don't bring up the subject of their delusions unless they try to inflict them on you, then politely tell them that you don't need, want, or appreciate their big steaming pile of crazy BS. And smile.

Know the truth and be Christian.

You go with your own mind, realizations and determinations.. as they do...

Why would what others think have any effect at all on what you think?

Study and make up your own mind... with real knowledge and support...

IMHO