Thanks Tagachi and Fly.
I'm aware of my perspective problem and I'm working on improving in this area. I will use the cone of vision and all the other tricks that result in a perspective without distortions. More cubes coming soon.
I will also do more life drawings.
For today I made another study from Rango. I focused more on the sky and I neglected the rocks in the foreground. I'm still having problems with drawing rocks.