Header Image for Mobile

Can the Header image be adjusted for mobile use in Sydney-pro by using the
Crelly slider ???
Also…why are the 2 Demo different:
One demo short version with a Responsive Header/slider-Image
https://athemes.com/theme/sydney/https://athemes.com/theme/sydney/
and click on “Demo”… http://demo.athemes.com/theme/?theme=sydney

And a long demo version not responsive:
http://demo.athemes.com/sydney/ http://demo.athemes.com/sydney/

As you can understand I want to make my header/slider-image responsive.
All help appreciated
Kind regards Leticia

Can someone please respond to this?