battery?

Hello, I've had an iphone 11 for almost two months and up to ten days ago everything seemed to be fine, until on August 23 the battery capacity drops to 99, but I don't worry so much comforted even by friends who having the iphone had reassured me by saying that it was normal, five days later it drops to 98, premise I try to charge iphone once a day.

3/10 now it’s 97