To be true Screen Overlay is basic feature used by almost every application.
Messenger Chat Head, Inbox Messages Preview and Whatsapp Messages Popups are all example of screen overlay feature, so you can't uninstall all application to resolve Screen Overlay Detected popups on your device...
You just need to manually turn off screen overlay of all applications in your device, Follow following settings to turn off screen overlay on your samsung:
>Click on More (Top right corner) & Select show system apps
>Turn off screen overlay of all apps one by one
This must solve the issue of screen overlay in your device...
If this isn't solving screen overlay issue in your device or you haven't got my answer then refer to below reference: