 Born in Duisburg-Beeckerwerth, Oestrich studied at the Technische Hochschule Hannover and in Berlin.After completing his studies, he first went to the Deutsche Versuchsanstalt für Luftfahrt in 1926, where he remained until he moved to Brandenburgische Motorenwerke in 1935.He became chief engineer of BMW after earning a doctorate at the TH Berlin-Charlottenburg in Berlin in 1937.