The first thing you should do is start with a completely blank project that has nothing, if you haven’t done that already.
Next, create a new player character controller and remove the capsule collision component. This is what makes the “player” collide and make contact with meshes and BSP that has collision. Obviously, remove collision from your meshes and BSP. You can remove collision from static meshes in the static mesh editor, just go to the collision menu and remove collision.