Loading outsourcing images

Hi

After settling my Clint site. He faced a string problem with the images.
First of all, he is a photographer and want to publish every event’s photos in his Website.
I suggested to him imgbb as it’s good and I see many photographers using it.
When he used it the photos are OK, but his Clint complain that the page need to refresh many time to load all photos.
How can I solve this problem? And what does it cause it to avoid it in the future?

– I use lazy loading in the website

The page I need help with: [log in to see the link]