This is a sample of how the image looks like when I finished to "erase" all the black part. It takes some patience and practice to do this. Use several sizes of your brush to erase the small areas. If you bought a one way ticket for this trip, actually you can stop here and save your image as it is right now. But as the same way we improved the sky, we also can improve the lower part of the picture. See next steps for this.