Start from the beginning like he was a new pup--- never mind what commands he knows, he'll get used to yours in no time if you show him what you want. Besides, all basic commands are the same for every dog - sit, stay, down, stand , come, heel etc etc. Sounds like a pretty good dog to me, Dobes that can be trusted the way he puts his trust in you aren't found every day. Sounds like the perfect dog to me.