Apple Watch Series 8 Problems

Hello, when I first bought the watch, I saw that there was a shadowy black defect on the strap, then when I took it to the Apple Authorized Service, they said that they could not guarantee my watch. Also, although they say that the battery capacity of my watch can last for 16 hours, the battery of my watch only lasts for 4-5 hours. But in wrist detection functions, heartbeat detection, sleep interval data ECG recording… I noticed a glitch in my watch. When I tried to apply for the warranty from Apple support, I got the answer "Sorry, we can't view your warranty data right now". I request the necessary from the authorized units.