Hello,
my server is hosted from Bulgaria. My question is: can i change the server country with: Romania,Russia,Macedonia,Serbia,Greece оr Turkey - with our neighboring countries ?

There is already answers on few threads about this, use search next time. No you can't change the flag unless your provider change its location. And changing flag will only confuse players when they come on your server and see it's not a language which they choose.

Locked.