Agree with all above and want to emphasize the value of obedience work. Group classes will teach you how to gain his attention in distracting situations. Such as people walking by on the street.
Your dog is acting normally and appropriately for a dog. Be fair to your dog and don't let him be exposed to such approaches when you are not with him. Can you have a friendly neighbour he knows be there with him when strangers enter? Or could they put him in a crate or another room then let him back out? His behaviour is not fair to repair men who have a job to do.