To do a hard reset follow the steps above:
1. Turn off the phone.
2. Press both the Volume Up and Volume Down
3. While keeping pressed volume Up/Down keys, press power button
4. You should see a RGB screen and then a message asking you to press volume up to do a hard reset. Do it.
5. Wait for the process to complete and you will have a clean phone.
If that won't work, you can try to flash the phone with the rom here:
Please do not forget to hard reset after flashing.
If even this will not work, you have a hardware problem and you should have your phone checked by a service.
Hope this helps.