Shadow mapping visual result not looking great

I’ve implemented Shadow Mapping in my program, but simply put: It does not look great, I know there are some graphical issues, but that is not the major problem.

What you see on the scene is a floor, a patch of terrain, a light indicator(!) to show from which direction the directional light is coming. Also on the top left you can see the depth of the scene, and right to it you see the scene rendered from the light’s point of view.

I know I have a bug in my Bezier terrain rendering, because in reality those mountains should be very smooth, but they have some weird bumps in them.

However I just think the shadow does not look right on the terrain itself, but I’m not really sure what is going wrong either?
Could anyone enlighten me and come up with possible explanations? I can provide code if you want, just not putting it out here now, because I do not know what parts are neccessary of my code.