FLATSOME THEME- issue with photos

Hi,
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 a little bit blurred, some of them fall out of the box in the category page(for this issue I’ve already come up with a fix but I’ll need to resize and crop some of the photos with Photoshop) and for some other pics the category box is too small if compared to the one I see in the flatsome 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. Isn’t there a way to modify sizes or change css in order to sort the matter out?
Of course I can provide you the website url.
kind regards
manuela