Thank you everyone for all the replies! I'm sorry i'm soo late in responding! Everyone has really good thoughts and I as I read them I was mentally reviewing what I do and don't do with him. Some of what was suggested I do with him already but still have the mouthy problem. The Central theme in the replies was a time out place, and the NILIF, which I do NOT do either of those with him. I will take myself out of the room and close the door but i never put HIM in time out. I am also not as consistent as I should be. I have found someone I think will be a good trainer for us and am starting with her the first of february. Though, I am going to institute a lot of the practices ya'll shared with me in the interim. This is the third GSD I've had, but the first, that was this assertive with me.
I will try to post an update once i start working with the trainer.