Adjust software and hardware keyboard settings on iPhone
If you have difficulty distinguishing characters on the iPhone keyboard or manipulating a hardware keyboard, you can adjust settings such as the key repeat rate.
Tip: Rotate iPhone to use a larger keyboard for typing in many apps, including Mail, Safari, Messages, Notes, and Contacts.
Change the keyboard settings for accessibility
Go to Settings > General > Accessibility > Keyboard.
Do any of the following:
Show only uppercase keys on the iPhone keyboard.
Adjust the key repeat rate on hardware keyboards.
Use Sticky Keys to press and hold modifier keys, such as Command and Option, as you press another key.
Use Slow Keys to adjust the time between when a key is pressed and when it’s activated.