Hello @buscape,
The size of product images can be managed through the WooCommerce settings. To do this, please go to Appearance >> Customize >> WooCommerce >> Product Images and adjust the thumbnail width according to your needs. For reference, please see the screenshot provided: https://postimg.cc/gnHpkgFz
For further information, please refer to our theme documentation here: https://www.8theme.com/documentation/xstore/woocommerce/product-images/
Best Regards,
8Theme’s Team