How to update my iPhone 6

iOS 12 is the highest version that will run on your 7 year old phone. Currently 12.5.4.

See the responses to your previous message→Want to update my iPhone 6 - Apple Community

Asking the same question over and over won’t change the answer.

You will not be able to update your iPhone 6 beyond iOS 12.5.4. If you need to run apps that require a newer version of iOS, you will need to get a newer iPhone model.

Didn't I just answer this question? You can't update beyond iOS 12.x.x.x on an iPhone 6.