How to start

[Nostrildamus]

I have problems to start the game. Yesterday the game started (I have no idea, what I have done, but it worked), then it crashed everytime, I wanted to complete the second singleplayer mission. So, I just uninstalled it and installed it again, because I thought it could help... But today I can't even start the game...

I have no logs about the problems yesterday, but it was at the second singleplayer mission, when the seraphim commander comes out of the gate. The game just froze, ok it doesn't really froze, there are aktive visual effect and i can hear the falling bombs of the fight in the background, but the commander does't came out of the gate. The only possible thing to do was to open the taskmanager and kill the gameprocess. Then, the gamewindow minimized itself and got grey. They told me, the appliocation doesn't answer.

Nja, I really hope this problem is gone now, but I want to play the game again. At first the singleplayer, to learn the game a bit.
But i am not able to open it again after installing it from steam.

How can i start the game?
Give me a step by step instruction please...

I know there are a lots of grammatical mistakes in the text, but that happens, if you're not writing in your native language^^


edit:
I am using windows 7 (I know, fa+Win7 is a bit difficult...)