Thanks for the additional information. I was just notified that a reply had been received. You don't need formal training classes but you do need formal training in that you train him at the same time for a specific period of time and go over the same command over and over again until he obeys the first time every time despite any distractions. The following site is helpful in helping owners train their dog. Be sure and click on the link to the page on obedience at the bottom. and links on subsequent pages leading to detailed instructions.
Training works best if you train at least 30 minutes a day (two 15 minute sessions). I would start making your dog work via the Nothing in life is free program (NILF). It is outlined below.
It will be helpful if you can find someone the dog reacts to who is willing to help you once you have your dog listening to commands consistently. What you will do is have your dog on the leash. You will have your helper off in the distance. Your helper will gradually move a bit closer to you preferably walking past your position in the distance. As long as your dog ignores them, you can give your dog praise and a treat. The second you see him fixate on the helper or show any other sign of aggression (hair standing up, etc.) give your dog a correction by giving a short tug and a firm low toned "NO". It shouldn't take your dog long to realize you will not tolerate the aggression and that if he ignores the other dog, he gets treats. Once this happens you can repeat the training moving the other dog closer until he is no longer trying to lunge or bark at the person. You will need to practice this when you and your dog are walking as well.
Bat training may help as well. Here is a slte that goes over this.
If you are feeling uncomfortable when a person approaches, your dog picks up on that feeling and in turn becomes protective and aggressive toward the person in order to try and scare them away or protect you. You really have to try not to feel worried. Often you will become worried even about how the dog might act and they will pick up on that as well. When that happens, they assume it is the approaching person you are worried about and have no idea that you are worried about how they will react and not the person. So try to keep the leash loose and don't tense up.
Keeping your walk at a brisk pace will also help limit the amount of time your dog is approaching and moving past the person and thus help stop the response.
I have seen some trainers move their dog to the side and make them sit and focus on their owners. This can be effective but your ultimate goal is to walk your dog and not stop every time a person approaches. Now when walking you can definitely keep a hot dog sliver in your hand and be sure the dog knows it is there as you are appoaching the person and walking by them. If he does well and doesn't growl bark or lunge, give the treat. DO NOT give a treat if the dog does any of those things.
I hope this information is helpful to you. If you would like any additional information or have more questions please don’t hesitate to press the reply to expert or continue conversation button so I can address any issues you still have . If you do find this helpful, please take this opportunity to rate my answer positively so I am compensated for my time.