how can i save my battery life

See if anything here helps.

About the battery and performance of iPhone 11 and later - Apple Support

iPhone and iPod touch- Battery Charging and Troubleshooting

Troubleshoot and manage high battery usage in iOS 9

sesehan wrote:

how can i save my battery life

Eric Root's suggestions are excellent. I would add one more.

When to charge your iPhone or iPad - Apple Community

I will also say that, no matter what you do, your battery will eventually stop holding a charge and need to be replaced. Batteries are consumables and there's nothing you can do to change that.