How many movies have Gertrude Welcker and Hans Adalbert Schlettow acted in together?

They have worked on 4 movies together! Their first movie together was Algol: Tragedy of Power (1920) while their highest rated movie together was Dr. Mabuse, the Gambler (1922). They have not worked together since Dr. Mabuse, the Gambler: Part 2 – Inferno (1922). They are most known for their thriller films together.