Best answer by Max
Sorry to hear about the apps issue with your P9 Lite phone.
Before attempting a factory reset, you can try to first wipe the phone's cache partition. As opposed to the factory reset, this will not affect your data and may solve your issue To do that, please follow the instructions below:
To do that, simply follow the instructions below:
1. Switch off the phone
2. Start pressing and holding at the same time the power button and the volume up button until the logo appears
3. In the new menu, using the volume buttons to navigate and the power button to choose, select Wipe cache partition, followed by Reboot system now. The phone will then restart.
For extra accuracy in entering the recovery menu, please remove the phone's protective case, if you have one. Also, make sure that you start pressing the two buttons at the exact same time and that you press the outer part of the volume up button. That way, you avoid accidentally pressing the volume down button as well, which will take you to a different menu. Finally, to ease the button pressing, hold the phone in landscape orientation.
Feel free to try this at your leisure!