and after this dog leaved him,my gs come to me and hide under my legs..and didn't wanted to move/or play with any dog around him..
i tried to ignore it,and do nothing..but he keep stay under my legs[i sit]..
There's nothing wrong with comforting your dog when he's scared. Don't baby him, just put a calm hand on his shoulder/back and keep it there for a moment. The contact really helps. Let him hide a little if he needs to hide.
how i can fix it,or make him more protector not for me..for himself ?
for me it's feel "shame" when the dog act like that..but in the dead line..i don't give ****.
my dog is more important for me,and i care for his health and life..and i put my ego behind,and want to try help him..just please tell me what to do?
He needs confidence to protect himself and be capable of telling another dog to stop harassing him. I wouldn't be at all surprised if his fear is actually attracting dogs that are bullies. I've seen it at the dog park sometimes: an overly submissive dog will attract the bullies, but when that dog gains confidence, they're not bullied. The dog usually gains confidence when they encounter dogs that are nice to them, play with them, and especially when their owners come to their defense (shoo the bully dog(s) away with an air of absolute authority).
If you cannot avoid loose dogs that try to bully yours, stand up straight, imagine yourself a giant wall of menacing authority, then tell the dog to beat it. If you have to, step in front of your dog and press on the offender. By press, I mean move forward unflinchingly. You don't have to be mean, just look like they cannot possibly get past you. Remember, a lot of dog body language is just appearances. If you act like you own the place, then as far as a dog is concerned, you DO own the place.
But those are all just bandaids. You need to build your dog's confidence.
Between the two of you, do training sessions. Lots of them. Teach him (or reinforce) some extremely simple command like "sit" so you can use it in stressful situations. Play some tug with him and let him win every time for a while.
Take him to places where there are other dogs and just walk by them from a distance. If he gets nervous, create a little more distance and ask him to do the simple command a few times. Then move closer.
Take him to places with people or somewhere else that he normally succeeds in navigating. Take him to other places that he really likes (like the woods or fields or some place natural if possible).
I'd also stick to socializing with dogs that are friendly, if you really want to. When they both start getting too excited, take a break. I have a feeling that the playful dogs might not actually be attacking your dog. They're probably getting too excited, too rough, and your dog isn't confident enough to know how to give off the signals to tell them such or is simply getting overwhelmed.
Jack was this way when he was younger. He'd be playing with other dogs and having a good time, then they'd get too excited and want to wrestle. He'd get scared and run back to us, hiding between our legs exactly as you described. We just had to keep reassuring him, and stepping back from the other dogs, playing a distracting game of fetch, then encouraging him every time he had a good interaction with another dog. Playing fetch helped a lot as it was something he could succeed at. It made him feel more relaxed and willing to give interacting another try.
Basically, this whole novel can be summed up as: set your dog up for success. Success breeds confidence.