Correspondence, monthly and school reports, 1927-1933; vows of secondment and instructions, 1928; beginnings of secondary school work in the Bukoba area, 1929; necessity of a central school and the the first steps towards this, 1929; reflections on the introduction of American Negro songs in Africa, contained in correspondence at the end of 1929 and the beginning of 1930; The consecration of our Kigala Church on 4th Advent, 1930; From the Growth and Becoming of a Haya Community, 32 p. ms.., 1932; Zur Frage der Centralschule, 1932; Correspondence and reports by Otto Hagena, 1934-1943; Versorgungsangelegenheiten, 1937; Musik in der Heidenmission, answers to questionnaires, 1939; Lieder der Bahaya, 1939; Curriculum Vitae of Otto Hagena, 1943; Condolences and condolences. Commemorative speech on the death of Otto Hagena, 1943; correspondence with Adelheid Hagena, née Johanssen, 1943-1958; death notice of Adelheid Hagena, 1970