This is a common Samsung Galaxy S7 error that can kind of blind side you. You start up an app for the first time and accept the usual permission requests. Then see a weird message that looks something like this:
So a screen overlay is a part of an app that is able to display on top of other apps. An example of this is Chat Heads in Facebook Messenger. But these screen overlays can cause you problems.
The easiest way to get rid of this confusing error message is to give in and follow its instructions. Go ahead and open up your Settings app. Then scroll down and tap Applications and then tap Application Manager. Then tap More to open the longer menu in the top right corner of the screen. Next tap, Apps that can appear on top. From here, scroll down and find the app that is requesting screen overlay. Once you’ve found the app in question, make sure the toggle next to its name is in the off position. Remember grey means that the toggle is off, green means that the toggle is on.
Keep in mind that it isn’t always immediately clear which app is trying to use screen overlay. Some of the apps that have been accused of causing this problem are Clean Master, Drupe and Lux.
In any case once you’ve made sure that screen overlay is turned off for the app in question, just go ahead and try using that same app again. If you’ve done this correctly, you’ll just be prompted to accept its permissions and then you’ll be able to download and use that app.
Let us know if you have any other smartphone issues you want us to explain how to fix.
Sources: Android Central