5-6 hours of actual screen time use seems reasonable. I mean my iPhone x was doing camera and video and i had to top up after 3 hours of continuous engagement... (100% to 20%) no surprise video is intensive ****.
Plus u did not describe what u actually do in day to day use but give a generic question so people are unable to help but give a generic response like “go to genius bar n get it checked upon” which I would say also because i have no idea what your actual core problem is... u nv know it could be a defective component and they might replace u for free since its still within the warranty apple period who knows no harm doing so. Plus if they ask u for a fee u have the right to decline the process. They will confirm are you able to to pay and proceed or not with upfront costs etc and reasons why... its apple.