I need to update my iPhone 7

1) You don't have enough free space on the phone and 2) you have the battery set to Low Power.

Try updating using a Mac or PC. Turn off Low Power Mode.

Update software on your iPhone, iPad, or iPod touchAppleOfficial Apple Support › guide › mac-help › mac

Update software on iPhone, iPad, or iPod touch in iTunes ...AppleOfficial Apple Support › guide › itunes › windows



Because:

Also, turn off the Low Power mode option.

Why can't you update the phone? What error message appears when you try?

A screenshot would really help, if possible.

What error message appears when you try?

A screenshot would really help, if possible.

We cannot help unless you provide some information.