I am not sure if they put down a temporary pitch over the normal one, or if like last time they are going to totally replace the pitch, but here is an Allianz Arena web cam that updates the picture every 10 seconds. You can see that they are rolling up the grass that was played on. I hope the old pitch is underneath, as it was just not right for months last years when the totally replaced it after the NFL game.

https://allianz-arena.com/en/arena/webcam/indoor

EEM