Hey Charline B.R. what a really nice drawing so far. The first thing i notice is that it seems to me like a one point perspective and not a two point perspective. All lines are pointing to one point (behind the right tower). Or is the other point really far to the left? What i see on your left tower is that the top of the cone is not in the center of the base of the tower. A vertical line need to run from the center of tower cilinder and the cone tip and bottom circle need to lay on that center line. I found a youtube video showing the principle: https://youtu.be/zkIYARAJVIA The roof of the tower is constructed of 2 cones that are overlapping, but both cones have their center on the vertical centerline. I hope my description is helping you in the right direction.