Not working on Mac - El Capitan software update

Good afternoon,

I bought the game with all the extensions yesterday on Steam. I haven’t done the updates for my mac software for a long time and i was more and more lagging, especially while playing at the game, so I decided to download the mac software update El Capitan to reduce it. But unfortunately, even if i don’t have lags anymore (at least while being on the net), I can’t launch the game. When I try to open it, the icon jumps but all you can see when you try to click on it is that the program does not answer.

Do you have a solution for it?

Thanks a lot,