Well first,it depends on why he’s biting. Aggression or playfulness? If aggression, I would use a muzzle or mouth restricting harness when he bites. After he bites,make a whimper sound like he hurt you and make yourself big, to show your dominance. Immediately slap their nose or tell them no. If it’s too severe put a muzzle on them for a short period of time or hire a trainer. If you don’t want to physically punish them, you could restrict them, like putting him in his cage.When I trained my moms pup I would also would hold her mouth shut (watch for the tongue) and tell her no.
My dog use to bite when she played rough, so I would use a nontoxic, non-dangerous but gross smelling and tasting thing on my hands. She hates garlic,so I would rub a bit of garlic paste in my hands before playing. Gross, I know, but very effective. Whimpering here’s would also help, most pups don’t notice when they start playing too rough, but they don’t mean your any harm so they’ll feel bad if you get hurt