don't worry bro ....just visit Samsung service center and flash your last firmware from them....you simply downloaded it by mobile data or wifi I think ....that was not proper procedure or recommended to install software bro ,,it damage software side sometimes and produce software holes....it's allaways need to be flashed by smart switch or by Odin or through authorised Samsung service center
Please perform the below mentioned steps to resolve the issue:
1. Adjust the brightness Settings > Display > Adjust the brightness.
2. Check device in safe mode:- Press and hold the Power key, when Power off icon appears > Press and hold the power off icon. Exit safe mode: Hold the power button and select restart on the screen.
For further assistance, register your concern in Samsung Members Application (Open Samsung Members Application > Get help > Send Feedback > Error report/Ask questions).
