There really is no way of knowing what temperment this dog has unless he has been tested and even then you won't know how this dog will react to situations until they come up. I would request a temperment test, most shelters have an employee that knows how to perform this. Ask for a 2 week trial period. If he passes the test, take him home. BEFORE EVER taking him into your home, once you get home with him, walk him for 30-40 minutes, then lead him into your home. Leaving the leash on him, allow him full access to the house and show him around. Training starts the second you takehim from the shelter. Arrange training sessions with an experienced handler (experienced with strong working dogs). Start the lessons right off the bat. Not only will YOU learn how to handle a powerful dog, but this also will create bonding time as well as teaching this dog who the pack leader is. Never yell, never hit. Be gentle. By being gentle, you will be showing this dog how to be gentle.