I feel Sebastian Mattukat is not convincing

Sebastian Mattukat as Writer in The Witch and the Believer (2021) made me pay attention more than I expected. Some emotions are too simple, and I cannot believe the character enough. For me, it does not feel very real in many scenes. The role needs more detail, but the performance stays on the surface. Many moments pass very fast, and I do not remember much after them. I do not hate it, but it did not pull me into the story. This is only my personal view, but the performance changed how I enjoyed the film.