Make mobile banner fit every phone

[GeorgeRizos]

So I added some code which uses 2 different banners, depending on if you're on mobile or on desktop. 

The only thing is that on some phones the mobile banner gets cut off on the top or sides, which cuts a bit off the '50%' or the white text on the sides. What code do I need to make sure that the banner will fit exactly for every phone, without making it blurry. 

This is my website: Thesnoozy.com