Adding correct lights to a cave

Hello everyone, i’m currently working on a school projects in VR and i’m building an environnement for it…

everything looks fine until I begin creating the cave, I don’t understand how to get the space totally black, there’s always a light in it… did I mess up something with my light parameters?

Another question (performance), is it possible to build a better shadow quality then this for a VR game?

thank you!