I cannot see opponent turn anymore.
It seems that it goes so fast that the map is black, even when I repeat opponents turn.
So now I do not notice anymore when an enemy hero enters the area that I can see.
Is there a way to adjust this, or should I reinstall?
Ingame click on 'System Options' and there you have the options of setting the speed of enemy heroes movement. The rightmost button there is for not showing hero movement at all. Thats most likely your setting so you can easily change it.