Hello david_cosmin,

@Hickory's answer pretty much sums it up. As the game requirements field says: https://www.gog.com/game/the_witcher_2

Requires the following packages: libc6:i386 libasound2:i386 libasound2-data:i386 libasound2-plugins:i386 libgtk2.0-0:i386 libsdl2-2.0-0:i386 libsdl2-image-2.0-0:i386 libfreetype6:i386 libcurl3:i386 and dependencies.

So you have to run these commands to update your system packages and then install game dependencies:

sudo apt-get update
sudo apt-get upgrade
sudo apt-get install libc6:i386 libasound2:i386 libasound2-data:i386 libasound2-plugins:i386 libgtk2.0-0:i386 libsdl2-2.0-0:i386 libsdl2-image-2.0-0:i386 libfreetype6:i386 libcurl3:i386

And like @Hickory said, make sure that the command won't remove any installed already packages.