Resizing product images

Hi! I keep changing the size for my product images in woo commerce/settings/products/show products (I have these titles in swedish so the translation may be faulty), I press save, and the head to add new product and then the settings are back to the original. I go back to woo commerce/settings/products/show products and indeed, the settings are back the original instead the altered ones that I put in there. I’ve tried several of times but it doesn’t work. My husband manages to make it work for the duration of creating two products but then it also kicked back to original settings. Can you guys please help me?