Select the backwards faces and use the "reverse faces: command in the contextual menu and get all the outward facing surfaces to be "front face" Yes, it can cause problems. If you don't see division edges between the reversed coloration, toggle "hidden geometry" in the view menu. Then you can reverse faces that are backwards separate from the adjoining smoothed faces. There are plugin tools to help this process if you have a lot of it, but that's the primary way to fix reversed faces.