If you have problem with your firmware or just did a bad update and lost other languages except Chinese and English, there is my method:
1. Enable phone debug in Developers mode
2. Run the A760_ command prompt (the one without 3 in the name)
3. Connect device to PC, choose Mass Storage and let drivers install
4. Click any key in the command prompt after driver installation
5. Phone will restart, stuck on loading screen and do the update
6. After completetion it will restart
If language is still missing, do the factory reset.