This puppy is old, about 7 years old. I think it was domesticated. You should take it to a pet hospital with regular immunization points. There should be an electronic chip around the dog's neck so that they can scan it for you. Then you can find the owner's information in the network system, including contact information. If you can't find the owner, you can send it to the pet rescue station, which is available in every city. I don't know where in Tianjin. You can search online.