How to change banner on Google Optimize for mobile version only?

Hello all,

I have a little challenge. I know it’s not directly related to Shopify. Namely it is about Google optimize. I hope someone can help me anyway because it’s about coding in general.

The question is: on Google Optimize, how can I change the banner in the mobile version without changing the desktop version as well?

I was added the mobile version via code by a Shopify expert and it all worked great. (See picture)

Now in the visual editor in Google Optimize in the mobile version, I changed the image via url(‘’…‘’), but it was then changed on the desktop as well. (See image)

Does anyone know what I may need to add to the CSS in Google Optimize or change in ‘‘edit HTML’’ so that the banner is only changed to the mobile version?

I would be very happy to receive feedback.

PS I have covered the logo and images.

Many greetings
Shano