if i search vinylhub by the name of a city, why apart from the region, some record store are listed in the results and most not?
The regional attribute of the shops is currently not indexed for search. If you see a shop show up in a search for a region (like the example you mention for Berlin) it is because the region (Berlin in this instance) is included in other attributes (like title, description and so on).
The best way to see all shops for a region is to navigate to that region from a shop that is in the area. For example for Berlin see: https://www.vinylhub.com/record-stores/Berlin-Germany
Improving the search results is on our roadmap, stay tuned.