Bring the screen within reach on iPhone
When you use supported models in Portrait orientation, you can turn on Reachability to bring items at the top of the screen down to the lower half of the screen.
Turn on and use Reachability
Go to Settings > General > Accessibility, then turn on Reachability.
To bring the top of the screen into reach, do the following:
iPhone X and later: Swipe down on the bottom edge of the screen.
Other models: Lightly double-tap the Home button.
To reset the screen, tap the top of the screen.