A German Shepherd Dog is actually herding dog. I think your uncle's dog is a bit of an anomaly. They should be good with livestock and small animals. I am not at all fond of mastiffs.
I'm not looking for one now--I have far too many dogs. I have four mini Dachshunds, the oldest 12, two 10 and one 8. When the oldest three Dachshunds go, I think I want another dog.
I also have a pit bull mutt who is just 3, but I don't expect he'll be very long-lived. I found him as 3-month old puppy, almost dead after being hit by a car. I took him to my vet to be put down, but the idiot vet went ahead and fixed him up without asking me and then gave me the bill. I can't believe I actually paid the bill! His leg was shattered in a million pieces--the radius, ulna and humerus were all fractured. He really should have been put down. I didn't look at the x-rays until long after, but she just put a cast on the leg from his elbows to his toes. Either she didn't see the fracture in the humerus above the cast--I'm talking about a complete fracture, even an idiot could see the two pieces of bone that should have been one--or she chose to ignore it and just patch him up. To fix the humerus with the shattered ulna and radius below it would have required surgery and she knew I wouldn't pay for that for a mutt puppy I found on the street. He must have been in incredible pain dragging that big wonking cast around with a complete fracture--two pieces of bone floating around grinding against each other--above that cast. He's a really tough dog. Eventually, the pain is going to be too much. He's an incredible dog, though. Really lovely temperament.