UINavigationBar does not overlap to UICollectionVi

问题:

I put Navigation bar inside UICollectionView in swift 4.
When I scroll the collectionView, it does not goes to back layer and it overlaps to Navigation Bar.

 self.collectionview.contentInset = UIEdgeInsetsMake(40, 0, 0, 0)

I also write this code but it does not work. I also unselect the "Under Top Bars" in Extend Edges in Attributes Inspector.
All the ways do not work.
Can anyone help me please?