Header Image not responsive?

Hello All, I am using Zubin Photography | Free Wordpress Theme Header Image questions:

1. When I bring in a new header image. It displays perfectly in edit mode but when published it is cut off and does not display full image. Is there a way to make it show full image as it is brought in?
2. How do I get this same image responsive and displayed across all devices from desktop to mobile? It displays full screen on desktop (but cut off) but when viewed on mobile it is severely cropped.

Can someone let me know if there is actually NO way of doing this OR if there is, point me to instructions on how to accomplish this? Thank you!!