Battery health problems

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Read this support article about iPhone battery and performance to learn about the battery health feature and what is considered normal performance --> iPhone Battery and Performance - Apple Support

"A normal battery is designed to retain up to 80% of its original capacity at 500 complete charge cycles when operating under normal conditions. The one-year warranty includes service coverage for a defective battery. If it is out of warranty, Apple offers battery service for a charge." A degraded battery may display the notice: "Your battery’s health is significantly degraded. An Apple Authorized Service Provider can replace the battery to restore full performance and capacity." If it is not at or above 80% "normal", consider contacting Apple about a battery replacement. --> iPhone Battery Repair & Replacement - Apple Support

According to the above quoted information, you could be losing almost 2% per month in the first year and until Apple would deem this to merit a warranty replacement.

Batteries cannot be repaired. Batteries are replaced.

You are asking us to guess at what your problems might be.