Hi,
Actually, all the CSS of HikaShop for the frontend is in the frontend CSS file that you can edit in the HikaShop configuration. And the documentation link Mohamed gave you precisely explains how to edit that CSS and how to find what CSS to edit in that CSS file based on what you want to change.
So what you're talking about:
at least give some pointers for us to find the parts of the CSS we are looking for
was already provided.
Please remember that we provide user support, that has always been the case. We sometimes give a helping hand and provide some bits of CSS but it's not possible to customize your pages for you.
And on top of that, we definitely can't give any precise CSS tips on a question like yours since with don't know how your page looks like, what is the CSS already applied to the elements by the Joomla template, the customizations that were done by you, or your template provider, etc. So with the information you provided in your message, giving the link to the documentation which explains you to edit the CSS of HikaShop and how to find what CSS to change in that CSS is the best we could possibly do.