In just two months my battery life drain by 3 percent

That's perfectly 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.

About Lithium Ion Batteries

iPhone Battery and Performance - Apple Support (IN)

Here are some tips on maximizing battery life.

Batteries - Maximizing Performance - Apple

Your Battery Health is excellent. Battery Health is an inexact figure that varies with usage. the typical Apple Battery lasts 2 years with normal usage. When Battery Health reaches 80%, it will be time to make an appointment at the nearest Apple Store for Battery Replacement. In the meantime, this link offers suggestions...

Batteries - Maximizing Performance - Apple