How to optimize iPhone 15?

Sorry, your question is a bit vague.

What exactly do you mean by "optimize" and "better than usual"?

The iPhone run as it's supposed to and has all the options to make it run as good as it possibly can. Optimization and cleaning apps are not advised on iPhones as they can't really access the OS internals to an affect any meaningful changes.

We are terrible mind readers, so we need more detailed information from you.

Better in what respect?

When was the last time that you had the battery replaced?