Hi and Welcome. My Name is ***** ***** I look forward to assisting you today with your question.
That update has corrupted the software of your iPhone. Your only option to fix the iPhone is, restore the iPhone to factory settings through iTunes by putting it to recovery mode, which will erase everything from it.
But if you had backed up your iPhone to iTunes on your computer or iCloud, then you can restore all your data back after restoring your iPhone from iTunes/iCloud. You can also redownload all your past purchases for free using the same account you used on it.
Follow the steps below to restore your iPhone by putting it to recovery mode.
First download and install latest iTunes on your computer from here : https://www.apple.com/itunes/download/
Then connect the iPhone to your computer with the USB Cable.
Open iTunes application on your computer.
On your iPhone press and hold the Home button and the Power button at the same time UNTIL you see a USB cable pointing to iPhone icon on the iPhone's screen. The iTunes will also detect a iPhone in recovery mode and ask you to restore it.
Click Restore or Restore and Update button.
Note : Put it to recovery mode while connected to computer and also in recovery mode your iPhone will show USB cable pointing to iTunes logo. And it will take a while to restore it.
Please let me know if that didn't work, so I will continue to help you until we fix the problem.