How to image optimize my Panino page?

I’ve set up a page use the Panino template. But unfortunately, its super heavy and takes a long time to load on mobile devices. I’d love to reduce the main images, but if I do that it won’t look good on the Desktop version!

How do I choose or size images for the template (say the top slider that uses full size images) so that they work for the desktop site, but then also are reasonably sized for a mobile experience? Does Upfront do this automatically?

It doesn’t seem to be doing it on my site, because again it takes a long time to load up.