DIrectional light shadow problem

I am completely new using UE5.
I watched a lot of tutorials but I still have the same problem when I add a directionel light to the scene.


As you can see on this picture, there is some problem with shadows : there is a lot of noise. It is the same before rendering in the real time view. Do you know how can I get rid of it ?
The scene is a .udatasmith exported from SketchUp.
Thanks for your help !

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