Battery health is getting abnormal

See this excerpt from the "Your battery's maximum capacity" section of the support article: iPhone Battery and Performance - Apple Support

"A normal battery is designed to retain up to 80% of its original capacity at 500 complete charge cycles when operating under normal conditions. The one-year warranty includes service coverage for a defective battery. If it is out of warranty, Apple offers battery service for a charge." In other words, if it is below 80% maximum capacity, it is below normal performance. Yours is still within normal performance range and a nominal 1% decrease per month of use.

Malakyasser wrote:

So do you mean battery health can go up again ??

No, it will never go up. Batteries are consumables. They will get used up and need to be replaced.

and also how can i improve battery health and maintain battery health

You cannot improve battery health. And, frankly, you can't do very much to prevent it from dropping. But, see here:

When to charge your iPhone or iPad - Apple Community

Malakyasser wrote:

how can i improve battery health and maintain battery health

To learn about maximizing (and the difference between) battery life and lifespan, read this support document --> Batteries - Maximizing Performance - Apple

Read this support article about iPhone battery and performance to learn about the battery health feature and what is considered normal performance --> iPhone Battery and Performance - Apple Support

If you purchased the iPhone in November, the Battery Health would normally be about 94-95% by now. That is because over a longer time period, the Battery Health declines an average of about 1% a month.

So, by next November you could expect the Battery Health to be at about 88-90%.

When the Battery Health is down to 80%, it will be time to replace the battery.

Please read the part above that says.......over a longer period of time, the Battery Health will decline an average of about 1% a month. This is normal.

There is nothing wrong with your battery. If you make an appointment at the Apple Store or authorized Apple Service shop, they will check the battery and confirm this for you.

It is not a linear reduction and the value does vary. In some cases you may even see it go up. The percentage you are seeing is totally normal and not an indication that you will continue to see a drop of 5% in the next week. Just make sure you have the Optimized charging settings turned on and enjoy your phone. Plan on replacing the battery in about 5 years under normal use and depending on the number of full charge cycles.

There is nothing you can do to increase the Battery Health. To maintain the best use of the Battery, just make sure you have the Battery Optimization settings turned on. Users have reported that the Health percentage has increased, but this action has nothing to do with anything that they have done and it just an artifact in the algorithm used to calculate the Battery Health or a change in the algorithm after an OS update. It is only an estimate and the observation you are seeing confirms that.