Medion LIFE P4310 soft resetJust take out battery and reinsert it.
Medion LIFE P4310 hard reset MD 98910
1. Power off the phone
2. Press and keep pressed Volume UP and HOME and press Power for about 2-3 seconds
3. Use Volume key to move to "WIPE DATA / FACTORY RESET"
4. Confirm option pressing BACK button
5. Move to "Yes --delete all data" and confirm pressing BACK button
6. After operation press Back button once again to restart phone.