So i closed everything up with brushes, but it stayes bright, but i want it to be dark, so it gets a spooky atmosphere.
Quick info: I just started to learn UE4.
Check the intensity of your DirectionalLight and SkyLight actors.
Most likely answer is skylight turn up too high, anything above 1 should be regarded with suspicion 
So, i deleted every light source, but i hasn’t changed much, it is still very bright.
So, i deleted every light source, but i hasn’t changed much, it is still very bright.
Then you either have a postprocess volume, or you have to rebuild light
If it’s not needed for the outside area, get rid of the Environment Color and lower Environment Intensity in the Lightmass settings (World Settings). Change the color to dark grey / black, and reduce the intensity.