Do i have to change some properties to my landscape textures?
Looking forward to your reply!
I have some suggestion for you, but maybe it come from your mateiral, if you want to take a screenshot so I’ll be able to verify.
But before I’ll answer to your question=>
- From what I know, landscape have their own lightmap resolution, but nothing more. (not 100% sure)
- Normaly, landscape material is like all other kind of material for the main setting. It’s all about how you make the material itself.
my solution for your material =>
- Multiplie the texture with the same texture (it will make it a little bit more darker).
- Mutliplie the texture with a constant (0,0,0).
- Use lerp to blend between your texture and a constant, use alpha to make it more or less darker.
- Multiplie the texture with a constant than lerp with the texture and adjust the alpha like you want.
My solution for your texture =>
You can open the texture inside Unreal and change the brightness of the texture directly, this will affect every material that use your texture.
You will have a darker result. I think they are other way to make the texture more/less darker (in the Material), but nothing more in mind.
If you have the issue again tell me 
Have a good day,
Gabriel
Hi and sorry for the late reply, here are screenshots of my Landscape Material Graph:![1]:
[alt text][1]
No problem, here some doc about lerp and multiply=>
You can ignore the Vertex Color and put a constant value on the alpha to control how it blend
If you don’t understand lerp, here a great explanation => https://answers.unrealengine.com/questions/150896/what-is-lerp-in-general.html
Your material is really simple (simple doesn’t mean bad), you can put a lot more thing to bring life. Material are very important, I think if you want to make good material you should see this => Intro to Materials: Overview | 01 | v4.0 Tutorial Series | Unreal Engine - YouTube
It is a basic tutorial, but I think this will help you, also when someone talk about a «node» that you don’t know, try to get information in the doc or try to use it in the material (you can type what you search in the right pannel).
Have a good day 
Gabriel