Hehe, Hanna, that's the sirious problem that you've rised in this topic and the roots of it are going to the Russian Revolution and to the beginning of XX century. There was the certain etiquette, you can learn it reading the classic examples of Russian literature of XIX century, but after the era of War Communism people were afraid to use it because the only adressing form to other person for using wich you usually shouldn't be shot was "comrade". That's why "сударь" and "сударыня" became archaic and "господин" and "госпожа" became weird. After the fall of domination of socialist ideology the adressing "comrade" became weird also so we have those the really weird one now: "man! woman! girl! young man!" and such... I'm personally very sad about that fact and very sorry for my language for being such fvcked and all those due political reasons, actually.