Site not displaying correctly on mobile devices

Since forwarding my domain name https://www.therocknrolldog.com to https://www.vegasrockdoglounge.hostawesome.com my site no longer displays correctly on mobile devices.

I’ve checked it by clicking the old site name https://www.vegasrockdoglounge.hostawesome.com and it looks perfect but when I use the new name https://www.therocknrolldog.com the header image is huge!

I’d appreciate any advice on how to fix this problem.

Sam