When I set the reponsive images, the main image is correctly showed (correctly adjusted)
But all small other images are expanded to fill the size of the page.(with bad resolution)

When I not set the responsive images, all the small images are not adjusted. Correct size.
But the main image is reduce regarding the page size but not in the both dimension.

What I need to enter in the responsive images CSS selectors to make responsive only the main image ?

Example of the problem https://www.ornicom.com/fr/produits/communicateur-ip-avec-telco-ipcom.amp.html