To work on the lighting, look at the shadow from the man. Then refer to the shadow on the foregroun rocks/cliffs. Start thee. Your light is coming from above and to the right and forward of your figures. SO the man' shadow should go back and to the left rather than forward and left. The girl should have shdow areas on her right side (left oriented to the screen. The sides and lower areas of the hands, her right face, the chest next to the bodice, and so on should have shadowed areas. It's easy to do as I suggested above with and upper layer, a softish brush, and a fitting blend mode, possibly a blur if your changes in depth of shadow end up too abrupt. Give that a try, just those two things. Then post your results. It's almost time to move on to a new project, but these areas are an important exercie and currently detract from the image. Don't be concerned; just make your shadows on separate layers so they are non-destructive.
Here is my suggestion for the girl. I use a 25% soft brush on 100 and 50%, then blurred it. Then I went back in with 100% soft brush and added more shadows. Then I used a soft eraser at 5-20% to soften some edges and fix the too much shadow areas. Brush, eraser, brush, and so on.
Let me know if you get the idea, or if you think it's even in the right direction. You or others may disagree, but that's what I would do. In fact, I would add yet another layer above to deepen some of the shadows or at least increase the opacity of my shadow layer which is at about 50% hard light.
EDIt: My eyes are tricking me. Just realized the direction of the sun. SO it is really the light on and from the cliffs that needs a different angle. So your people casting shadows are OK. But the girl does still need shading and I hope you understand the idea. Imagine the location of the light and see how it casts its shadows. It's that simple. My apologies for confusing the issue.
One more thing. The shadows cast by the models have harsh edges. As I mentioned above changes are less abrupt. Also they need to be deeper/darker right up next to the people as the light would be much less available there. To soften the edges, use a softer brush, or even something like an animal fur brush to soften those edges to the grass.Here is also where a blur can help. Often after you make a blur, you need to go in and repaint some of the deeper shadow areas as the blur can spread and lighten them more than you want.