what needs to improve?

your bodies great, just need definition... Define your biceps, mid section and back and you'll be a BEAST..only body part that should blow up would be your chest and your chest is decent right now. I don't know your workout routine, but from experience at 17 all you probably want to do it lift heavy and for you it should be the opposite. More weight less reps for gaining and less weight more reps for cutting and defining. This is all obvious stuff, but at 17 im not sure how much advice you've been given.
 
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