It says that my battery has a unknown part

Well, the additional information that you have provided pretty much explains things.

The phone has been damaged. This is not going to be a fix-it-yourself deal.

Make an appointment at the Apple Store or take the phone to an authorized Apple Service shop to let them run some checks and go over your options with you.

You can find a list of authorized Service shops in your area by using the link just below:

Find Locations

Doe the phone still have its original battery, or was the battery replaced at some point in the past?

Tap Settings > Battery > Battery Health > Maximum Capacity

What is the Maximum Capacity?

Good luck!