How do I turn off the screen overlay from settings?

A

AC Question

After I installed the last software update yesterday, I couldn't download photos on whatsapp , couldn't make calls through Messenger, and couldn't open My Gallery as well as some other Applications.
All of the above due to a Message displayed first that i have to turn on permission through settings and when i tried to turn on through permissions of Application another message displayed that i have to turn off screen overlay first through settings.
Whatever I do nothing solve my problem.
I don't know whether the problem is in the latest update or not .
I need assistance.
Thanks