Hi everyone! We saved and picked up a male puppy from the street (he was going to be ran over on a highway) since he was 8 weeks old, apparently he is a mix of german shepherd and unknown or another type shepherd, he already has all his shots and in his last visit to the vet everything was fine. He is a very hyper puppy, he is currently 5 months old, I walk him everyday for about 35-45 mins. When I walk my puppy he automatically sprints forward until the leash stops him, he then proceed to calm down and stay behind smelling stuff until he feels like sprinting all over the front again. I tried a lot of leash training recommendations, such as allowing him to smell and see everything he wants until he is done, I've tried restricting his interactions, I've tried to motivate him to walk with my with very good treats but he totally ignores them, I've tried to stop moving until the leash is loose again but give it up since it took forever to move 1 block , I've tried changing directions unexpectedly but he keeps pulling and sprinting wherever he wants to go, I've tried running on the opposite direction so he can follow me but it ends in him strongly bitting my ankles . I've tried collar and harness Leash; long and short. But he still sprints forward pulling the leash, stays back and pulls the leash back way and then sprint forward full speed to the front and repeat everything all over again. He is not my first dog, but he is the first one that has shown this type of issue with the leash. I understand that he still being a puppy requires time and patience, but I am seriously concerned that I am not doing it properly or If I will be able to see any results with any of the methods I've already tried. Something that bothers me too is that he will grow into a big and strong dog and if I am not able to correct his pulling, walkings will be terrible for both of us. I am already starting to develop some back pain from his pulling, even though I don't pull him back, the strength I use for restraining the leash from escaping my hands is enough to cause me back pain. I am honestly kind of desperate because I don't know if I will be able to fix it. Thanks for reading my long post and all your help will be appreciated.