Dark screen.

I haven't played the game for a long time. Now I have a little free time. I started playing simple maps against the computer. I chose a standard map that was already included in the game (I also downloaded some maps). The problem is that at a certain point – after saving, the opponents start moving, one of them attacks me, and a battle begins. The battle starts, but the problem is that it's very dark. The objects are distinguishable, but you can hardly see anything. I had the same problem a while ago in the campaign on my computer (I gave up). Now I'm playing on my laptop. Does anyone know what the cause is? Or can you help me? I can give you my save file, you can play through it, a not-too-difficult battle will occur, and then you can save it again and send the new save file back to me...