Well I hate to be the bad news breaker but American pitbull terriers are known for being bad guard dogs because they’re SO PEOPLE FRIENDLY… it would be a different story if other dogs came into your house though. Dogs well known to be good guard dogs also are slightly more inclined to bite people are German shepherds,, Rottweilers and Doberman pincers… they were bred to protect and don’t normally hesitate to hurt people in their way. I’ve known many who were both trained in multiple languages and some who just naturally were very territorial not always to a fault. My apbt is protective of me for no apparent reason but he’s very friendly to everyone unless someone rough houses me too much such as family members. APBT’S are known for aggressive towards DOGS not people. I cannot stress that enough. If you weren’t looking for a good loveable companion dog who loves people then maybe you should probably consider finding the puppy a Beyer more suitable home.