@ xiaolin:
you`re right, the cancellation on the card is Warszawa. But on the handwritten text on the backside I can read: Wyszków, the town of the sender. The text is harmless, and there is nothing to read about the ghetto. The card was probably dropped in Warsaw, 40 kilometers vrom Wyszków away.
Gruß kartenhai
Thank you very much, I have queried the information from the Internet.