Amtrup made his professional opera debut in 1932 at the Landestheater Altenburg. This was followed by many appearances in Meißen, Neisse, Wilhelmshaven, Hanau, Bunzlau, at the Staatstheater Schwerin (state theater of Mecklenburg) and until the end of the Second World War at the municipal Städtische Bühnen in Chemnitz.
