Image sizes with Storefront

Hello –

I’m using your theme Storefront. Hopefully it is not a problem I’m asking for support here.

I want to change the image sizes keeping the displayed sizes the same, I guess with CSS.

I haven’t have a problem before this but now somehow I cannot set the sizes via a 3rd party plugin Symbiostock (as I used to), so I need to solve it with Woocommerce or Storefront somehow.

The task:
There should be 1 image in the same size for “Image catalog thumbnails” (Which I see on the shop / product archive pages) and for single product images.

Currently as I see it would be sufficient to have only 1 image size which Woocommerce / Storefront uses everywhere.

Optionally, I like to have another small thumbnail size, which appears e.g. at the checkout / cart pages, widgets. — But this is not that important for now.

What do you think, Is there a solution for this?

Thank you in advance!