Xiaomi Air Fryer Not Functioning Properly

My son gifted me the Mi Airfryer with a capacity of 3.5 liters. The courier delivered it on November 14, 2023, at 6:00 PM. The next morning, I opened it and baked some pies in the oven, while the remaining four were cooked in the Airfryer. I set the manual control for 20 minutes and checked it from time to time. The top part of the device turned brown, even burned, but the bottom part remained completely white. I attributed this to inexperience since it was the first use. Today, I fried two small potatoes, set the timer for 25 minutes, but the bottom part remained raw, and the top part burned. Three hours later, I sliced the potatoes thinner and placed them directly in the tray, setting 25 minutes for the potato frying mode. Again, there were white spots. I manually added another 5 minutes and cooked it for 30 minutes at 200 degrees, but the result remained the same.