The wall shadow error,I don't know why

Make sure that meshes (like the ceiling/wall) do not extend beyond each other, if they do then the part that’s beyond the corner can receive light/shadow that can bleed inside. Also, it helps if your walls have an outer surface to block light from entering.
Other than that, it looks like you need to render at Production quality, also make sure that you have a Lightmass Importance Volume.