How do I download this game on my Galaxy SII smartphone?
It's impossible to download this game on a Samsung Galaxy S2 smartphone because it hasn't been developed for. However, there is a version of 7 Wonders created for mobile phones and it's called: 7 Wonders:Magical Mystery Tour. You can use the link posted below in order to access it.
Note: You can trigger the installation from web or using the Play Store on your phone.