how do restart my ipone

See the following from Restart your iPhone, iPad, or iPod touch - Apple Support

If it doesn't respond, see Force Restart from the same link above.

How to restart

1. Press and hold the Sleep/Wake button until the slider appears.
2. Drag the slider to turn your device completely off.
3. After the device turns off, press and hold the Sleep/Wake button again until you see the Apple logo.