Hi thanks for the comments, for the big scene with the city i have finished this in 3h to make the full scene, the others scenes take 1h in general modelling and photoshop.
the time depends on the complexity of the scene.
For example for the full view of the city i have all the layers separated, for the lights, the fog, and the sky because after its a long work to be done.
i have to animate all the lights in the city, the effects, and i have to put too, a lot of flying cars in the city......so this scene its one of the most complex for the moment...