If you need more time to respond to a notification or messages that are visible only temporarily, you can adjust the time before they disappear:
If you’re unable to use a touchscreen, Switch Access lets you control the phone using external switches or keyboard keys to select items, scroll, enter text, and more.
To use Switch Access, you must have one of the following:

Follow onscreen instructions to select:
To adjust options for Switch Access later, go to Settings > Accessibility > Switch Access > Settings.