Took a look and there is a few easy to fix problems.
- Your light map resolution per static mesh is to low (set tot default 64) so this is preventing your shadows from being fully formed or generated into the light map at all. If you select the static mesh there should be a resolution over ride and should be changed to a value that gives the asset the most amount of coverage. For testing to see if you can dial it in change to 256 > 512.
Note this will increase light build time if you make your light maps to big per object so only use high values to test that it’s working.
- The green surfaces is being caused by the renderosity effect of the directional light bouncing off of the hill side and splashing off the back face of the building. This is actually a normal effect of the directional light as to the number of bounces. To mute the effect you need to control the over all environment lighting as to indirect lighting by adding a sky light.
By changing the intensity of the sky light or decreasing the directional light you should be able to get a good balance between indirect light and light bounce.
More than anything though your landscape is one big sheet of green so if you paint it properly that should get rid of 99% of your problem.