From the Wikipedia article on "Tintin et Moi" :
The film is based around Numa Sadoul's revealing interviews with Hergé from the 1970s, and goes into detail about Hergé's life and how Tintin affected it.
The film is based strongly around Hergé's experiences and state of mental health leading up to the writing of Tintin in Tibet, often heralded as Hergé's most personal album. The history of Tintin is examined through Hergé's life and the way that he was affected by the growing popularity of his character.
The underlying theme of the film would appear to be the way that Hergé's, or rather Georges Remi's, private life affected his work—for example, Bianca Castafiore is an unconscious (or perhaps conscious) reflection of Georges' first wife, Germaine, and the way that Captain Haddock responds to her reflects the way Georges often felt towards his wife—specifically, the mothering instinct that Germaine had toward him is shown most explicitly in The Castafiore Emerald. The subject of religion is also discussed, including Georges' gradual disillusioned view of the Catholic church, and the opposition he came up against due to Wolff's sacrifice in Explorers on the Moon. The influence of Chang on Georges' work is also highlighted, using reconstructed footage and actual archive footage of their meeting in 1981.
Hope that's of some help !