Short answers, pulled from the story.
Hermann Kallenbach was a Lithuanian-born Jewish South African architect, born on the 1st of March 1871, who became one of Mahatma Gandhi's closest friends and associates. He donated a 1,100-acre farm near Johannesburg to Gandhi for the Tolstoy Farm, served as manager during Gandhi's 1907-1913 satyagraha movement, and accompanied Gandhi on his final voyage from South Africa to London in 1914. Gandhi described Kallenbach as his "soulmate."
The Tolstoy Farm was a community near Johannesburg that housed the families of satyagrahis during Gandhi's nonviolent resistance struggle in South Africa. Kallenbach donated his own 1,100-acre farm to Gandhi in 1910 for this purpose and personally chose to name it after Leo Tolstoy, whose writings had deeply influenced him. Kallenbach also abandoned his wealthy lifestyle to live on the farm alongside Gandhi.
Kallenbach was interned as an enemy alien when World War One broke out in 1914, ending his plan to accompany Gandhi to India. He was held as a prisoner of war on the Isle of Man from 1915 until 1917. After the war he returned to South Africa and resumed his architectural career.
The rise of Nazism and Hitler's antisemitic propaganda prompted Kallenbach to rediscover his Jewish identity and become a Zionist. He served on the Executive Board of the South African Zionist Federation and planned to settle in Palestine. At the request of Moshe Shertok, he visited Gandhi in May 1937 to seek his support for Zionism, though the two disagreed on the issue.
Kallenbach's cremated remains were buried at Kibbutz Degania in Israel. He left a portion of his estate to South African Indians, directed the bulk toward Zionism, and gave his large book collection to the Hebrew University of Jerusalem.
The Gandhi-Kallenbach Archives is a collection of private correspondence between Mahatma Gandhi and Hermann Kallenbach. The Indian Government purchased the archive in July 2012 to prevent it from being auctioned by Sotheby's, stating that the correspondence belonged to the legacy of their cultural and socio-philosophical leader rather than to private profit.