I was buy iphone 12 pro max 07th February 2021 , why very decrease my battery health? My battery health is 95% now.

That is very normal for a 1 year old phone.

iPhone Battery and Performance - Apple Support

When it gets down to 80%, get the battery replaced

Smilin-Brian wrote:

Apple won’t replace the battery under warranty until it has reached 80% capacity. 

Apple won't replace the battery under warranty unless it gets down to 80% capacity (within the first year..)

That's pretty normal. Rechargeable batteries inherently lose capacity as they're charged and recharged. Apple's battery longevity rating is for a typical 80% battery health after 500 complete charge-discharge cycles, although the way they define a "cycle" (full and/or combined partial cycles added together) isn't necessarily the ideal way to calculate expected wear.

If one estimates maybe 25 cycles per month and 1% per 25 cycles, after 11 months the expectation would be 89% battery health. Now you could be using your battery less than that, but 95% is still pretty good.

nomu132 wrote:

How to get battery replaced, when limited warranty ended?

Through Apple or an Apple Authorized Service Provider is the most common answer around here. Not sure where you're located, and whether or not you have access to an Apple Store. That's my preferred way.

If you're really concerned now, it's my understanding that Apple will replace a battery on demand even if it's not under 80% as long as the customer pays for it. And any repair parts done while in the warranty will assume the remainder of the warranty or 90 days if that's longer.

Sounds normal. 😉

Apple won’t replace the battery under warranty until it has reached 80% capacity. 

Good point, Chris! 😉