I want to update my phone

If you own iPhone 6 as your signature suggests, the highest level iOS version it can run is iOS 12.5.3. If you are looking for the newer iOS versions, your phone released now 7 years ago, is too old, too under powered and incapable of being updated higher. It's time for a newer more modern iPhone if you need the newer versions.

Your iPhone 6 has half the memory of the iPhone 6s. The iPhone 6s is the oldest iPhone supported by current iOS software. iPhone 6 is not. There are no hardware upgrades. Your only option for newer iOS is a newer or new iPhone.