Full size images load on product page despite thumbnail exist

I am using some theme on Woocommerce for my shop but since the same is behavior is the same for Storefront, I expect this is ‘standard’ behavior. Which surprises me and makes me think something is wrong with my setup.

So, on product page images are always loaded with their biggest sizes, not thumbnails. For example, on page https://www.elvistudio.ee/modern-kiss-print-gold-art/ GTmetrix always shows error:

“https://www.elvistudio.ee/wp-content/uploads/2020/01/Modern-Kiss-poster-in-black-frame-on-the-wall-scaled.jpg is resized in HTML or CSS from 2560×2560 to 485×485. Serving a scaled image could save 333.0KiB (96% reduction).”

despite that i have 485x485px thumbnail in my media files.

Same does not happen on catalog pages, for example, https://www.elvistudio.ee/product-tag/gold-art/ which contain same product and GTmetrix is fine with it.

On product page I expect large (2560x2560px) picture to load only when I click on it (Lightbox) since magnify is disabled.

How to fix:
1. so that 485x485px or other thumbnail is used instead of 2560x2560px resized to smaller size
2. how to load large size (2560x2560px) only on demand, i.e. on image click – when Lightbox opens.

Current behavior is very bad for SEO as page load time is significant because of large images.

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