While there, he took a minor role in Lewis Milestone's 1930 anti-war film All Quiet on the Western Front.
[4] In 1934, director Robert Siodmak, who had fled to Paris after completing Brennendes Geheimnis, made it possible for Kohner to contribute to the screenplay for La crise est finie.
During the Nazi era, Kohner was not credited for his contributions to the screenplay Viktoria, an adaption of a novel by Knut Hamsun.
For his contribution to the 1938 Deanna Durbin comedy Mad About Music, Kohner received an Academy Award nomination.
[5] From 1939 onward, he worked only sporadically writing screenplays; among them was The Men in Her Life with Loretta Young and Conrad Veidt.