Biography and autobiography are actually a form of fiction since much of the details are not true in fact

Thay's actually false, perhaps a biography might have some exaggeration things but for the msot part a biography is considered non fiction because it is a story of a real person's life told by someone else and an autobiography is a true story of a real person's life told by that real person themself like a documentation of what they did so that is false biographies and autobiographies are non fiction.