Any suggestions on what I can do about my dogs aggression issues?

I have a two year old American staff. My concern is that every time I take him out he wants to fight other dogs. One time he somehow pulled away from me and actually started fighting a pitbull in the middle of the street. I really don’t know what to do. He doesn’t really listen to me because he was my brothers dog and I recently got him.

Any suggestions on what I can do before be gets seriously injured? Or vice versa…