How do I update my iPhone to get Gmail?

The iPhone 7 Plus, which originally ran iOS 10, cannot update to iOS 16 or highet. It lacks hardware that all of the iPhones that can run iOS 16 or higher have, and for it, iOS 15.* is the end of the line.

Google has chosen to make their GMail app require iOS 16.0 or higher. This means that you cannot use the current Gmail app on your iPhone 7 Plus. If you want to use Google’s app, you must buy a new phone.

A workaround may be to set up another e-mail app, like Apple’s Mail app, to work with your Google e-msil account.

The iPhone 7 is not compatible with any iOS version higher than iOS 15 I am afraid. If you're in need of a higher iOS version, you're in need of a newer iPhone I am afraid