Unable to install update. An error occurred installing iOS 10.3.4

Hello Roqsta,

Thanks for reaching out to the Apple Support Communities! I understand that you are having an issue updating your iPhone. I'm happy to help you find some information.

Here is a resource that can assist you with troubleshooting steps:

Get help with iOS updates

If you have an issue after reviewing the link, please let me know.

Have a great day!