Why did black spots appear on the model when transferred to Unity?

Question

Unity

I made a model in the Cinema4D program, when transferred to the Unity game engine, black spots appear on the model (see picture). This is definitely not a shadow, I tried to turn them off. The file extension with the fbx model.
Does anyone know what could be causing this and how to fix it?

Answer 1

the normals are wrong, maybe you should recalculate in the editor