How my battery’s back to normal

Batteries degrade over time with usage due to chemical aging, that's just how they work.

You can expect about a 1% drop per month with average use on an iPhone.

Apple recommends replacing it when it reaches 80%. To check your battery health, go to Settings > Battery > Battery Health.

iPhone Battery Replacement.

https://support.apple.com/iphone/repair/service/battery-power

About Lithium Ion Batteries

https://support.apple.com/en-in/HT208387

Here are some tips on maximizing battery life.

https://www.apple.com/batteries/maximizing-performance/

When was the last time that you replaced the battery in your iPhone 7? If you have not done this, it is likely long overdue.