My iphone won't turn off and I've lost the settings icon

Try a forced restart

1. Press and quickly release the volume up button.
2. Press and quickly release the volume down button.
3. Press and hold the side button.
4. When the Apple logo appears, release the side button.

The Settings App cannot be deleted. Slide over to the last page of all your home pages to the App Library and you'll find the app there. You can move it back to any home page you want.

Your tag line says you own iPhone 6s with iOS 13. Is that correct? If yes, press and hold the side power button until the slider to power off appears.

If your tag line is incorrect and you won a newer iPhone, please specify which model it is.