My iPhone 6 keeps going on random apps without me touching it and screen freezes when I am typing

Try to reset your device. This won't delete your data stored on this device.

• Press and hold the Sleep/Wake button
• Press and hold on the Home button
• Keep holding both buttons until the display turns off and back on with Apple logo on it.

Multi-Touch Repair Program for iPhone 6 Plus - Apple Support

Restore your iPhone, iPad, or iPod to factory settings - Apple Support

Reset the hardware (hold the power and home button till the screen goes off and comes back with apple logo). release the buttons when you see this.