It is not easy to read the film title on the poster. But I got many film program folders from my parents from the 1960s and know the movie offer of this time very well. The person on the poster looks like a doctor, so it could be the comedy Dr. med. Hiob Prätorius. And look here at postertreasures I found the shown East German poster.
Dr. med. Hiob Prätorius was a 1965 West German comedy film directed by Kurt Hoffmann and starring everybody's darling Heinz Rühmann and Liselotte Pulver. It was based on a play by Curt Goetz - one of the most brillant comedy writers in the German-speaking world.
The story tells about an older doctor and a young woman in trouble.
The same play was filmed by Joseph L. Mankiewizc in 1951 as People Will Talk with Cary Grant.
The movie started on January 14th, 1965 in West German cinemas and came already on August 13th, 1965 to East German cinemas. It was the most successful West German movie in 1965. So I am sure it was also very successful in East Germany. And in the evening the street before the cinema was full of people - more than on this postcard.