Hi Jafet, nice to hear from you.
As you can see the flow you need i.e. display products only of that specific user (vendor), in the category page is not supported by default. Hence you have to do custom code and add this.
We don’t have any ready made code for this custom requirement. So you need to develop this on your end, by checking whether a user is logged in. If yes, fetch his user_id and from there corresponding products.