Pit Bull puppy with newborn?!?!

Brittany
I need some pit bull moms or just anyone who has owned one before to help me out. I have grown up with German shepherds and poodles and I love all dogs. However, my fiancés mom came across a pit bull puppy that was going to get sold at petsmart if it didn't find a home and begged my fiancé to adopt it if she paid. He and I talked about it and I agreed. But I honestly have never met such a bad ass little dog. I know HE IS A PUPPY but he has the worst personality to me. He's sneaky, he's defiant and just has no chill all the time. He's six months old and I'm wondering if he will be okay when he have a baby in September? I just honestly don't know because I've never had one.