Sound & display problems

[Middlefing3r]

I downloaded the game, started playing and it was all good till map ends ....
then statistic screen appears and when button ready show up to click it and start playing again
I clicked it then my game moved to background of windows
Using alt + tab i come back to game but got same problem
So i restarted game and now i also dont have sound ......

Please give me some hints