Fantastic updates Zou! the faces are expressive and neatly drawn, the landscapes are really good and the oil painting is lovely. I agree that the values on the cliff could be clearer, but I geuss a scan/photo flattens colours alot, does it look like it has more contrast in real life? But really I think you just need to add bits of finishing details, like on the trees and concentrate on bringing out the values and darkening the foreground and adding some more bits of detail to draw the eye into the picture, too much detail on the cliffs could be too distracting.
Very nicely done though, you have good oil technique