Genes of a mixed puppy

Hello, a friend is selling several puppies.

I have doubts if I can buy one because of their genes.

They have a dad which is a mix of a Rottweiler and a German shepherd. The mother is a black labrador.
They look great. They are black and gray.

My goal is to raise a puppy to be a personal protection dog for me on the criminal streets of Brazil. So it needs to be trainable and have guts.

Not the dad seems to be protective and strong. But the mom is not only a Labrador, which may be too friendly for protection work, but she is also a very scared character. She is affraid of everyone and everything.

Can I buy one of their puppies and raise it for my personal street protection, as well as being a family dog.?
I am willing to do a lot of training.

And is a mix like this a healthy mix? Or will it have diseases when it gets older?

I must finally note that I really like going outdoor s in nature and also do a lot of swimming. So that maybe a good feature of the Labrador;