How to recover my files and personal data a phone who doesn't boot? My Galaxy S II runs under Android 4.12 and it is stuck on the boot screen. How can I recover my files and personal data on the phone ?
Is the Phone rooted and is USB-Debugging enabled?

If yes, you could probably boot into recovery and try recovering the files via ADB. 

How to copy selected files from Android with adb pull shows you how to work with ADB to recover your Files ;)