I will briefly inform you about hard resetting iPhone 7 Plus, one of Apple's big screen devices.

To hard reset iPhone 7 Plus;
Make sure your charge is over fifty percent.
If you have dealt with charging, turn off the device.
Then press and hold the power button. While holding the key down, hold down the volume down key on the left.
When the Apple logo comes, release all keys.
That's all you need to do. The phone will reset itself. Wait for it to come to the splash screen. Finally, you can install the device and start using it again.