yes, these words are still used. 'Gospodin' and 'gospozha' were kind of forbiden words in USSR , but its dissolution, these two came back and now are commonly used instead of 'tovarisch'(=comrade) Well actually it is more of a written and diplomatic/business style. You probably won't face them a lot in the spoken language. Though you can here "Дамы и господа", it's "Ladies and Gentlemen" in English. Вы можете использовать и "потому что", и "так как", зависит от контекста.