How can I tell if my GSD has a good temperament?

Okay, I bought a GSD about5 or 6 months ago... when he was 8 wks old. I don't know the breeder, but I somehow found him. He had a boy GSD. Supposedlym his father was a champion showdog and mother was a farmdog from chile. So I umed the pup would be one of the best temperaments. I bought him for $500. I thought it was a steal. His name is Turbo, and he is the sweetest dog i've ever seen. I am trying to teach him stuff like sit stay down and he knows them but is a little stubborn sometimes, but he seems to be improving. People come play soccer in my backyard and he runs and plays with them. Never bit any of my friends. SOmetimes though he growls and barks at strangers that are a little bit far away in public. He also barks at dogs. We have another dog- a bichone. Turbo is alot bigger. IDK if hes playing but he kinda jumps on his hind legs and puts his paws on her a little. He never actually bites her. She hates him. She runs away and when turbo jumps her she shrieks and snaps. IDk if turbo is being aggresive or just playing. When anyone tries to pet him he is great. So... is this a good temperament of German Shepherds? if not what should i do?