Steps required to install counter-strike 1.6 on you Android device.
1) Install CS 1.6 client.
https://play.google.com/store/apps/details?id=in.celest.xash3d.cs16client
2) Install Xash3D FWGS.
https://play.google.com/store/apps/details?id=in.celest.xash3d.hl
3) Download game files.
https://cdn.cs-boost.lt/cs/CS16-Android.zip
4) Launch CS 1.6 client and choose game files directory (the files from Step 3)