He re-built the Leineschloss, the Marktkirche, and the opera house all in Hanover after the destruction of World War II.
From Berlin they moved again to Hanover after his father was appointed professor of turbine technology at the local technical college.
For instance, after completing high school he worked, as part of his practical requirements, at the construction site of the Oder-Dam as a carpenter.
The strict objectivity of the Bauhaus building in Dessau, which Oesterlen visited in the years before he started his architectural degree, made a lasting impression on him.
There he initially studied with Heinrich Tessenow, but changed a semester later to learning from Poelzig, who was at that time regarded as the best teacher of architecture in the Weimar Republic.