How to LazyLoad & Resize Background & Flip Box Images?

Dear Forum Members,

We have found that background images and images in flip boxes on our website do not lazy load nor do they resize for mobile/tablet devices:

Our site is built using GeneratePress and the BeaverBuilder plugin.

In other words, the background images rows are coming from BeaverBuilder.

The flip boxes you see on our site, e.g. home page, are built with Ultimate Addons Lite for BeaverBuilder:

Would you have any suggestions how we can lazy load and resize the background images and the ones the in flip boxes?

We have tried various lazy load plugins and Image CDN services but find they all fail.

We have, however, found one that solves both challenges:

You can see optimole in action on our testing/staging site:

For various reasons, we would rather not use Optimole, which is why we are asking for your help.

Kind regards,