Complex sentence: Olga Deterding was educated at Oxford, but in 1956 she volunteered for unpaid work at Dr. Albert Schweitzer's leper colony in West Africa, where she continued to work until the latter's death in 1965.
Split into simpler sentences: Olga Deterding was educated at Oxford, but in 1956 she became an unpaid volunteer at Dr. Albert Schweitzer's leper colony in West Africa. Deterding remained with Schweitzerwas, where she continued to work, until the latter's death in 1965.