How to get my GSD to now be over protective?

I have a GSD.he is 2 years old this summer he will be three.i have a big problem.from the first few minutes of his first time here he begun to be over protective about my family,especially me.he follows me everywhere i go.if i go to the toilet he sits outside the door waiting for me.he only goes asleep alone!its insane..when my friends come over and we mess and play fight he growls at them so basically we either go outside or stay locked up.on walkies its worse.when he sees a dog he freezes and wont move.when the dog gets closer he barks and tries to brake out and its hard for me to handle such a powerful pet.he doesn't growl at my next door neighbor for some reason..it is really starting to annoy everybody and when i tell him to go away he goes away for a few minutes then comes back.on walkies he isn't this obedient so i used a choking collar but it didn't work.and i really don't want to hurt my baby with these spiky collar thing..but if i have no choice i will have to.he is REALLY obedient at home except the "leave me alone" command.like i say roll over and he AUTOMATIC LY is on the floor rolling over.if i say fetch and trow a ball he is chasing after the ball then comes back and sits in front of me ready to give it to me to do it again.so i really don't get him..there aren't any training lessons around my area.