How to fix this weird shadow?

Hi, I’m newbie for unreal engine. Now, I am facing a problem about a weird shadow. It appear both on above and under every object. And the shadow also appear on left and right of the screen. You can see the result in the picture below.

I try to tick and untick many checkbox which relate to lighting but it does not help. I don’t know what is going on. It seem that this weird shadow appear in every camera angle, that make it so strange.
If you need more information about this problem, please tell me. I hope that I can fix this. Thank you.

That’s a reflection, not a shadow.