How are you applying the image to the scene? Through a Billboard? A video material in Unreal? Looks like it’s going through a keyer….

Yes, I exported the project from Unreal

Is there a way to import images that use transparency ؟

I think the problem on unreal

I think the image should be exported from Unreal  as if Decal 

Yes, as I expected.. the material must be converted to Decal .

No, it doesn’t have to be a Decal at all. Use a Translucent material and it should work.