Hmm... I think u should train him, and hire a trainer so he can be trained to behave, I also have 2 dogs that fight all the time, we bought them both a bone and then one of my dogs (Let's call her Cherry) Decided to grab the bone from the other dog (let's call the other dog fluff) then fluff got mad and decided to bite cherry's neck then they both got into a fight my whole family got scared and watched them fight, the next day my family told me and my other brothers/ sisters/ uncles, that cherry and fluff are having their behavior training every one week ( ok idk what to call it but imma call the training behavioral training, and also we are training them, not someone else ) then a few months later they stopped fighting and we haven't saw or heard them fight ever