I cannot log into Q-Store using my account I created on the regular shop.
When I’m trying to create an account (on Q-Store) using the same email address I get this message:
Error: An account is already registered with your email address.
Any way to resolve it, please?
Use the password reset option for q store login. It’s an issue with linking accounts to both sites. Ask for a new password at the q store login and make it the same one as your other login for simplicity
It worked. Thanks a lot! 
Add this to the list of things to clarify and made easier. Spending the day cleaning up support articles, website copy, etc.
This is probably a dupe of:
https://subliminalresults.com/t/password-synchronization-between-q-and-normal-store/6083
You can login in the main store first and then open the q store. That way works for me.