Samsung Grand 2 backlight dims

Hello, please help. Yesterday I bought samsung grand 2 duos, today I noticed that backlight dims slightly and in a few minutes becomes bright again. And this despite the fact that I turned off Auto mode and power saving.
Can someone faced with such a problem
Thank you in advance


I have the same problem, and I took it to the service, and they gave me new device, also Samsung Galaxy Grand 2, and this one is also reducing the screen brightness and in few minutest, goes to the original settings