The second problem I have is following one: The installation fails due to ther fact the DirectX cannot be installed. Everytime when it comes to this point - the installation is aborted and the game files are gone.So I have DirectX11. Maybe some one has a solution. I managed to play the game - simply ignoring the error message and starting the game - and by "killing" the installation task. What have I done wrong?
You have done nothing wrong :) Hmm... The current installer requires the internet connection to download DirectX which in most cases is needed to run the game (even if you have DX11). So my hypothesis is that you had no internet connection or it's firewalled (of DX download server was temporarily down).