I want to update my phone battery health .. so please help me

You are approaching the 80% mark at which you will need to make an appointment at the nearest Apple store for battery replacement. You might also turn on Optimized Charging. Check this link for tips...

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

To update it you need a battery replacement from the local apple store

Good day!

You might want to check this:

https://support.apple.com/kb/index?q=battery+health&src=globalnav_support&type=organic&page=search&locale=en_US