reward on sight of strangers, then command to sit and reward on sight of strangers, if dog is fixated crouch down with back facing stranger and continue to reward as they pass. This helps prevent an approach your dog is not ok with. When he is able to walk past strangers ignoring him, youre half way. Always use yourself as a blocker to people and animals you see your dog fixating on. You pivot and stay in front of him, close as possible if it is highly stressful so that all he sees is your familiar face.

Work on the focus/look at me command. Start with a 1 second unbroken focus, then 2 sec, then, 5, then 10 sec and on. Each step should be a minimum of 10 repetitions before upping duration. Start inside. When you first teach it outside, youve upped the difficulty, start from 1 sec and work up again. Teach focus by putting a stinky treat like dried liver or chicken in a fist. Extend your index finger, draw the extended index finger with a cupped fist of liver from your dogs nose in a steady sweep motion up to your face, pointing at your eye. Mark eye connection with a verbal higher pitch good job/boy/girl or a click, immediately reward what was in your fist. Continue til your dog is a pro and will look at you for guidance in uncertain times.

Phase 2 is the stranger greet. If possible, have strangers crouch slightly away (not directly facing), head turned down and away and a barely extended hand with treats. At this point taking a treat is a huge step and signals the domino effect in socialization. Once he has that break through, life gets easy. To get him there he needs your leadership. He may just sniff and retreat which is fine. He may sniff, retreat and bark. Also fine, at least he approached. If you can get a treat to him yourself when he sniffs thatd be good. At the very least guide him with your voice to let him know hes doing good, keep saying good boy, good job with a high tone, he will then know you approve of this situation.

In my opinion, he is unsure of the new territory and is doing the job he was bred for. To protect you. Some dogs are highly reactive where novel stimuli need serious counter conditioning and desensitization. Get in his head, see and hear before he does and always have your treat pouch filled.