I have doubts.

0I know that's correct:02br
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001) She was at the cinema. ( yesterday )02br
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002) We will meet at the club.02br
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003) I always meet someone I know at the doctor's.02br
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004) There are lots of shops at the airport.02br
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005) I stayed at the hotel.02br
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00But I want to know how to say that I'm in the place right now ( in the building ).02br
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00Can I say:02br
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001) I'm in the cinema ( now, I'm watching the movie ) or I'm at the cinema.02br
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002) I'm in the club ( now, I'm drinking a drink ) or I'm at the club.02br
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003) I'm in the doctor's ( now, I'm waiting in the waiting room ) or I'm at the doctor's.02br
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004) I'm in the airport ( now, I will fly soon ) or I'm at the airport.02br
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005) I'm in the hotel ( now, I'm at the reception desk ) or I'm at the hotel.02br
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00Maybe these are stupid questions, but I'm not sure which sentences are correct and which are not. For example when I go to the beach I say:02br
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00I go for a swim at the beach. 02br
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00But when I'm there I can say:02br
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00I'm on the beach sitting on a towel. ( I'm at the beach sitting on a towel. I quess this is wrong. )0-