Battery of my new iPhone drains very fast

Apple provides these tips:

Batteries - Maximizing Performance - Apple

You can try force closing all apps. Typically this is not needed, but some apps do consume more resources than others using Background Refresh.

Close an app on your iPhone or iPod touch - Apple Support

Plug the phone into the power adapter and leave it connected all night.....every night.

Few users are aware that the "charger" is in the phone. It automatically regulates and controls the process. It is impossible to overcharge the battery.

The battery works really hard when the phone is new. After about a week, things will calm down.

You are plugging the phone into the power adapter at night, and leaving it connected all night.....every night, correct?