hm i tried it, but that will be not the problem. it adjusts the brightness,thats right. however problem is, that on pc there is light like in middle of day, but on mobile render the object is completely dark 
if i display the volume samples (Show - Visualize - Volume lightning samples) its strange that i dont even see those little rectangles, even one. But why on pc it renders good then?)
edit: i am using the directional light (which produces most light, the other lights are quite weak)
edit2: now i see its related with Cast Shadows options (on Directional Light). If unchecked, there is no light, if checked, there is light on mobile, however, i have problems to light the whole scene, even if the landscape is almost flat. is there any trick to make just everything on the scene bright?