A stubborn doberman... never...
I could be mistaken, but it sounds like you are a stranger to the dog still, and you are having a hard time relating on his level.
If you've never been through handler training either in a formal class, or by a trainer you know, that is where I'd start. Some are better than others, but most of them are a very good start. It isn't perfect, but as a big box chain that you can find almost anywhere in the US (not sure where you are at), I can recommend petsmart puppy classes as being pretty good.
With a new dog, there is a time commitment for bonding before a dog will do something just out of mutual respect. I generally crate train for when I can't be home, but I try to be home as much as possible, and I literally live with new dogs and puppies on a 6 foot lead. Eat, sleep, shower, bathroom, you name it, the dog is with me. I show it where to do its business every 30 minutes at first then gradually less often, and I work on lots of petting and saying sit when the dog sits, down when the dog is down, etc. After a while, the dog will follow you anywhere you go and trust you without reservation. Then when you start teaching, the dog has a vested interest in it because of mutual respect.
Beyond that, patience. He may not understand yet, or you may just still be a stranger to him. And if you are hesitant to take a class, please just do it. It isn't a dog class, it's a handler class, and it will impact every dog you ever come in contact with for the rest of your life, not just his.