I have checked your gallery page and in browser console / performance chart I find our that most of the loading time with huge amount of timeouts generate mailchimp-woocommerce-public.min.js
I guess you have some mailchimp subscription widget or mailchimp and woocommerce integration which slow down this page.
Gallery js and css files are compressed it’s couldn’t be a reason of any delay.
I have checked your gallery images, you don’t have huge images in your gallery so it’s should load very fast.
Try to disable temporary this mailchimp / woocommerce integration temporary just to see difference.
You should find the reason of this delays. It’s could happen in the case if website server have some network problems when it’s connect with mailchimp, because it’s external service. It’s just my guess.