Hey Hermann 😊
You’re right and good eye catching that. The nose feels flat because the mid tones are missing. Try softening the bridge edges and add a gentle shadow under the nose wings instead of outlining them. Also darken the nostril core just a bit for depth 👍
Overall the eyes and lips are strong. Fixing those nose values will push the realism a lot 🙌
Give it a small pass and share an update 🎨