I have been trying to update my iPhone 6 but it is not working
iPhone not always backup why ?
i tried many times to update my iPhone but it’s not working
Question marked as
An iPhone 6 will only update to iOS 12.5.5.
If you’re “there” … no further updating is possible due to hardware constraints of the “elderly” phone.
Re: backing-up, see this article for available options:
How to back up your iPhone, iPad, and iPod touch - Apple Support