how can i fixed may battery health unknown part

There are 2 possibilities:

• Your original or Apple replacement battery has failed
• You replaced the original battery with a non-Apple battery that does not have built-in battery condition monitoring.

Apple will replace an original battery for free if the phone is still in warranty or has AppleCare+, or for $69 if it is out of warranty→iPhone Battery Replacement - Official Apple Support. The can usually do it in an Apple store while you wait.