DIfferent hero image in desktop & mobile

Hi,

I love your theme! As can be seen from my link, I am almost finish.
One issuse cropped up during my testing.

My desktop and mobile view is showing different image.
I would want the desktop image to display on all devices.

Is this a bug or something that I did wrongly on my side?

thnanks!

The page I need help with: [log in to see the link]