Final answer:
Leni Riefenstahl's first movie is not specified in the provided information, but her most influential work, 'Triumph of the Will,' illustrates her significant impact on cinematic technique and documentary filmmaking.
Step-by-step explanation:
The first movie that Leni Riefenstahl made was not explicitly mentioned in the provided information. However, it is well-known that Leni Riefenstahl is a prominent name in filmmaking, particularly for her work on Triumph of the Will, which is a documentary of the 1934 Nazi party rally in Nuremberg.
Riefenstahl's work signifies an essential evolution in cinematic technique and the documentary form. While this film is not her first, it remains one of her most discussed works due to its powerful propaganda during a time when films were used to influence public opinion.