If you have difficulties with hand tremors, dexterity, or fine motor control, you can adjust how the iPhone touchscreen responds to tap, swipe, and touch-and-hold gestures. You can have iPhone recognize faster or slower touches and ignore multiple touches. You can also prevent iPhone from waking when you touch the screen, or turn off Shake to Undo if you unintentionally shake iPhone.
Go to Settings or > Accessibility > Touch, then tap Haptic Touch or 3D & Haptic Touch.
Choose the touch duration—Fast or Slow.
On an Use AssistiveTouch on iPhone