Sign in Screen Image not full


Device: IPhone X

We have defined an image for the background on the Sign In Screen but it does not cover all the screen.
It misses the characteristic “round corner design” spaces of the screen shape.

Is there something that I am missing?

What shape and resolution is your image?

Tried several. Definitely is bigger and in glide backoffice preview looks good but not on the Iphone.
Are there any good practices regarding shape and resolution?