I train dogs as a hobby. All types & sizes. What you're experiencing is normal and the little guy will learn via positive training & several chew toys scattered around while he's teething.
Mouthing & chewing on you and other things is normal. When you catch him chewing someting he's not supposed to, do not say no or yell at him, but quickly put a chew toy in his mouth and then praise him.
Make a big deal out of saying "good boy". Give him the positive strokes he seeks. Be sure you always use just the two words "good boy". Consistency is the key for anyone who is working with him. They learn much faster with positive reinforcement as they do want to please you.
Dogs being pack animals will test you early on by nipping at you. This is biting which is not cute. Especially if I'm training a Doberman or other large dog. Here's an easy solution.
First be mindful & expect it. Once he nips at you, again don't say no or yell. But turn to him as fast as you can grabbing him with both hands on the excess skin on the sides of his neck, quickly lifting him off the ground. This is done being silent & scares any dog, since they are in the air & have no control.
Hold him up a few seconds & he'll calm down. If he barks or persists, say no firmly as you give him a little shake. He'll understand he's not to bite after you do this consistently. Sometimes I only have to pickup a dog I'm training three times before they get it and stop, others take a bit longer, this works perfectly.
After all it's not "cute" to have a biting problem with a 100 lb. Doberman.
Once your dog knows you and your family are the alpha figures he'll know his place and be very civilized.
Hope this has helped you.