I made the most ridiculous thing. I accidentally disabled both remote logins and database accesses for the Administrator accounts (including the one with Windows Authentication (Administrator account) and sa account on the production server! Please tell me a way that there is a way to access the server with administrator privileges! :(

Is it possible from an installation or some kind of command line etc?

Again, Administrator account IS disabled for SQL Server (but I have remote connection to server, the account itself is working...) So I literally cannot access to the sql instance with admin privileges.