Responsive header / hero content

Hey guys,
I have been struggling with this problem for hours now and can’t find a solution.
I use the free “Fotogenic” theme and have a problem with the responsive header and its image.
It works perfectly on my mac and on the mobile simulator in the browser and in WordPress.
But once I open it on my iPhone XR it shows me the image in full size and won’t be responsive to the mobile browser (Safari or Chrome). You will see just a small blurry part of the picture.
I tried to use custom CSS like:

.mt-fotogenic-frontpage-hero-image-wrap  {
  	width: 100%; !important;
		height: auto; !important;
		
 }

Still not working. Thanks for any help!

• This topic was modified 3 years, 9 months ago by Jan Dembowski. Reason: Moved to Fixing WordPress, this is not an Developing with WordPress topic

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