How to use different image sizes for featured image in a slider extension?

I realized that responsive/scaled up images are not being used by the following slider plugin.
https://www.ads-software.com/plugins/advanced-bootstrap-carousel/
Is there anything I can do to set scaled up versions of the image/different sizes to be used, such that it doesn’t negatively affect mobile performance.

• This topic was modified 4 years, 10 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]