Consumer to consumer

That’s because themes just control how a website looks, not how it functions.

You should be looking for plugins instead, like https://www.ads-software.com/plugins/woocommerce/

What you want is called a “marketplace”. https://www.ads-software.com/plugins/search/marketplace

Thanks for the answer.
But,
I don’t want a Shopping Cart!
I would like a site, where people can upload there second-hand goods with price, and if someone would like to buy it, he or she has to write to the seller for it.

Here’s another possibility. Use a plugin (like Formidable Pro) that lets people create custom post types from a front-end form. Their contact info, images, text, etc., would be part of the form and resulting post. You could have categories, tags, etc.

The trick, of course, is to make sure that sold items get removed.