Samsung Galaxy S6 black screen with x, what can I do?

[AC Question]

Samsung galaxy S6 black screen with x

Suddenly my Samsung galaxy s6 has turned into black screen with x. When I do power and Volume down button for 15 seconds then it reboots but same black screen with x at the right or left corner appears. I tried to connect t fast charger but no joy.
After couple of hours screen came back alive for 30 seconds and then again it gone back to same black screen.
I had updated Andriod Marshmallow and its OS version is 6.0.1 Recently there was Samsung security patch as well.

 

[lucianus_luciferus]

this issue was already discussed in several threads
please use the search forums function to search for your problem first and you will find more
check out one of them HERE