How to open a room? I asked my girlfriend for it. Do I need an ID card? what can I say?

To get an ID card, you need to open a separate room first, and then let your girlfriend find you. Or you checked in, got your room card, said you'd come back later, and then went up with your girlfriend. In fact, the people in the hotel are not so stupid, they know what you do. Asking too many questions will only make them mind their own business and generally won't be wordy.