Responsive Grid hardest part was the hero/nav

So I can't figure out how to get the hero image to overflow on the bottom only, stacked overflow wasn't helpful. I tried to do two background: url, url but background doesn't overflow so I set one to background and then put the top image in the div but still can't get it to overflow on the bottom. Also the nav I think I did the box shadow wrong I don't think it's suppose to be a box-shadow on it. Any help would be amzing! Oh yea then the calc property for the font I got a bit confused trying to do that