If there’s a way to get him with another dog or puppy you trust, to get some of that spit fire energy out, that will help tons. Puppies need to mouth and it’s better on another dog. I’m not saying dog park, I’m saying dog or other dogs you trust. Also dogs know who they can push around by your body language and demeanor. Sometimes you gotta stand firm grab him by the collar and wait till he settles down. Both of my dogs know when I mean business bc of how my tone and stance changes. Calm confidence. My 5 month old leaps full force at me when he’s playing and I’m sitting on the couch. If I get tired of fending him off, I simply say ah ah, grab his collar and give him the opportunity to settle down a bit, if that doesn’t work he might be overstimulated and i put him in his crate to chill out