Changing the structure of the site, when there are several cities?

Question

Search Engine Optimization

Situation: there was a gymbalance.ru website of a gymnastics school in St. Petersburg with good positions on St. Petersburg requests. This site has a section of articles, separate pages for each branch in St. Petersburg and other information pages. With the opening of branches in Moscow, a website appeared on the msk.gymbalance.ru subdomain , also with an article section, separate pages for each branch.
Now the question arose to rewrite the site and lay the correct logic. As an option, make a federal page gymbalance.ru and subdomains for each city msk.gymbalance, spb.gymbalance.ru and others, for the projects fest.gymbalance.ru, magazin.gymbalance.ru.
Questions:
1. Is the idea right? Is there a better way to link all projects, cities under one name?
2. How to minimize the drop in search traffic primarily for St. Petersburg, because gymbalance.ru will have general information, and spb.gymbalance.ru will be a new subdomain. What about the information pages and pages for each St. Petersburg branch, their domain will change, right?
3. Is it better to combine a block of articles under the main domain, or is it better to leave your articles at each subdomain?

Answer 1

Good afternoon!

1. Yes that's right. Your logic is correct. Subdomains of your site are already normally ranked by regional queries in Yandex.
   
2. You create a subdomain on "spb" with relevant content. And see how in this case the search engines will rank your St. Petersburg queries. If they are re-ranked to a subdomain, then you can easily rewrite the main breeding gymbalance.ru.
   
3. Information pages are in no way tied by their queries to regions - they are geo-independent. Therefore, it would be logical to leave them on the main domain.