How can i keep my battery health good

The typical Apple Battery lasts about 2 years of normal use. When yours reaches 80%. it will be time to make an appointment at the nearest Apple Store for a new battery. This link may help...

Batteries - Maximizing Performance - Apple

Battery Health will only do one thing.......decline. The trick is to minimize this.

Make sure that Optimized Battery Charging is enabled on your Phone

Plug the phone into the charger and let it charge overnight, every night.

See: When to charge your iPhone or iPad - Apple Community