I do not understand the original post properly. All I can guess is it may be a troubleshooting error.
This may help:
http://support.apple.com/kb/TS1702
Come out of all overlaying screens, force close the APP STORE on your device, restart your device, re-launch the app store, make sure your signed into your iTunes account, not your friends. Make sure no other apps are downloading at the time, start a fresh download of Battle Dragons.
The paid app your friend downloaded onto your device, delete it if you have not already.
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