Yes. Goodbye Christopher Robin takes elements from the actual experiences and relationships of A. A. Milne and his son, presenting a fictionalized account of those true occurrences.
It is indeed based on true events. The movie depicts the story of how the Winnie-the-Pooh books came to be and their impact on the Milne family's life.
Yes, it was. Goodbye Christopher Robin was inspired by the real-life relationship between A. A. Milne and his son Christopher Robin.