FLATSOME--photos are blurred despite following all instructions given

I’m building a new ecommerce store using the flatsome theme which is great but I’m experiencing some issues when it comes to uploading photos. I’ve already set sizes as suggested in the theme documentation and then regenerated thumbnails but to no avail.
Photos are still blurred, some of them fall out of the box in the category page and the category box is way too small if compared to the one I see in their demo website.
I’ve already contacted the theme support but their answer wasn’t helpful at all.
If somebody could give me a suggestion I would be grateful.
kind regards