Any time there are cases of potentially aggressive behaviors (growling, lunging, snapping, biting) it's important to seek the assistance of a dog behavior professional. This is for safety and the correct implementation of behavior modification which requires a certain level of skill. Usually, I would work on such cases using methods based on desensitization and counterconditioning https://pethelpful.com/dogs/Dog-Behavior-A-Guide-t... (after taking a careful history of what the dog perceives as "threatening)", where care is taken to not send the dog over threshold https://pethelpful.com/dogs/Dog-Behavior-Understan... and aiming to form positive associations. In other words, I would pay close attention to the dog's body language for the most subtle signs of stress, while I would guide a person to move towards you in a calm manner first, then increasingly with more decision, while the dog is being fed high value treats. I would then progress or take steps back based on how the dog responds. I would be aiming to attain a positive conditioned emotional response. Of course, this is just an example, so a disclaimer is warranted here, do not try this on your own, but please consult with a dog behavior professional using force-free behavior modification methods for safety.