My iphone its battery health were down 79 to 76 about one month please help me about why my iphone are faster down to 76 help! Please

You are way overdue for a battery replacement. Apple recommends replacing it at 80%.

Batteries degrade over time with usage, that's just how they work.

You can expect about a 1% drop per month with average use on an iPhone.

Apple recommends replacing it when it reaches 80%. To check your battery health, go to Settings > Battery > Battery Health.

iPhone Battery Replacement.

https://support.apple.com/iphone/repair/service/battery-power

Please go through the following links.

• iPhone Battery and Performance - Apple Support (IN)

Protect & Prolong the life of your iPhone's Battery: Batteries - Maximising Performance - Apple (IN)

Try some of these options too.

1. Avoid Screen Mirroring
2. Put on Low Power Mode
3. Put Auto-Lock on (1 min):- with the Low power mode it will be 30 Sec
4. Disable Push notifications for apps you do not use often
5. Keep your iPhone Facedown to prevent notifications to light up the screen
6. Enable Auto-Brightness:- Settings > General > Accessibility > Display Accommodations > Auto-Brightness [Enable]
7. When possible, manually lower the brightness from Control Center
8. If you want to watch continuous Videos/Movies. Stream it on TV or a Monitor
9. Don't force close apps; Apps that are not on the frontend screen are paused by the system to save energy. Apps require more energy to re-launch. Apps that are open in the background use large memory is a myth and quitting them is counterproductive
10. Location services may please be allowed only while using the app. Avoid the "Always" option wherever available
11. Set your iPhone to fetch email & Calendar data from the internet less frequently
12. Turning off Background App Refresh 
13. Charge before it drops below 20-30%
14. Try connecting to trusted Wifi wherever available instead of a Cellular
15. Enable Airplane mode in areas with bad cellular and wifi coverage. Your phone keeps trying to reconnection with the missing/weak network. Searching uses energy
16. Switch off Wifi & Bluetooth while Roaming or Not in Range
17. Enable "Wifi Assist" only where a good Cellular Signal is available: Settings > Cellular or Settings > Mobile Data > Wi-Fi Assist [Enable]
18. Periodically Check the Battery Health (Settings > Battery > Battery Health)