Your latest figures are so elegant!
Regarding your landscapes, what exactly are you trying to achieve with them? Landscapes can be used to study varied subjects. They're one of my favourite ways to study colors. In this kind of study you don't actually need to worry about rendering stuff, you either do thumbnails or big images with broad brushstrokes. The point here is to get the right colors by eye, with no color picking from the original. Aim for 30 min studies.
But the trick is to keep questioning everything: Why do these mountains look blue? Why isn't this shadow merely green + black? Question everything, try to figure out how the world works. Pay attention to how a color relates to another, how placed side by side they look like different colors. Then you'll be able to create, not only reproduce.
As it was pointed before, your perspective looks a bit off in these studies. A quick tip is to start from the ground. Be aware of the horizon line, and bear in mind that the farther something is, "flatter" it'll look:
Knowing where the ground should be, then proceed to shape the terrain. Work on your mountains, hills and valleys, but never forget the underlying perspective. If you feel uncomfortable with perspective basics, do some cubes on the side. They're fun!
To speed up your organic rendering studies, focus. Do separate studies of foliage, rocks, moss, water, and put everything you've learnt together later.
Lastly, remember to switch between studies and things from imagination. As forrestimel mentioned, remember to apply what you're learning. (: