Hello,
Understood, now for your question if you have identified the command responsible for the problem, no need to locate it, just take it again & adjust it to your needs, and put everything at the very end of your Css file.
This should be enough to override the command you want corrected but to be sure you can add a Class or an Id html to increase his priority, example:
#hikashop_category_information_menu_218 .hikashop_product_listing_image {
width: 25% !important; // Or your required command
}
Regards