During World War I, he worked at different military offices in Pskov and Vitebsk.

In 1925 Riga German Landlord Society elected Bielenstein as a secretary.

In 1931 he became member of the board of the Riga sickness fund.

In 1939, he together with majority of Baltic Germans moved to Germany.

In Riga he designed more than 30 residential buildings, mostly in a rationalistic form of Art Nouveau, though some of his buildings also bear influences from Latvian National Romantic style.