Can you imagine painting this scene as a series of layers that progress from light to dark? The lightest area is the sun, just about to disappear below the horizon. Let's call that white. The next lightest area is the open sky. It's the part that's yellow, darker than the sun, but lighter than the clouds. So, we have sun, sky, then clouds. Then comes the ground plane, which is darker than the clouds but lighter than the trees and phone poles. Got it? Sun, sky, clouds, ground, trees.
Each layer could be an overall wash, covering the whole page except the parts of the previous layers that you want to save. Here's the image with the color removed. This might make it easier to see the relative values:
Here's another image that behaves well as a series of layers. Choose one of these two and make a monchrome value study, that is, a simple version of the scene painted with only one color. Let the study dry between layers so your edges are all hard.
Feel free to round up or down so you don't end up with too many values. You should have no more than five for these studies; white, light grey, middle grey, dark grey and black. Use a color straight from the tube, no mixing. We're trying to focus on value, so we'll ignore color and edges.