I feel Arne Schumann is not convincing

I watched Oskar's Dress (2022) and Arne Schumann was one of the parts I kept noticing. The role needs more detail, but the performance stays on the surface. Some emotions are too simple, and I cannot believe the character enough. For me, it does not feel very real in many scenes. 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. Maybe other people will like it more, but this is my feeling.