How to stop annoying big Notifications I use a Samsung Galaxy 7. OS is Nougat.

Previously notifications used to be small texts in notifications area.

Now I get an annoying small popup window for every app upon notification.

Any ideas how to stop this?
I think you're referring to Heads-Up notifications (those notifications which pop up on the top of your phone's screen).

The following methods have shown to completely disable them for all applications while maintaining regular notifications in the status bar. All of these methods are free. Some require a rooted device and some don't.

Non rooted devices


ADB method


Firstly install minimum ADB/Fastboot setup. You can find more instructions here: New To Adb And Fastboot Guide.
After enabling USB debugging, connect usb cable from device to computer.
Open command prompt (right click + shift) and enter the commands:


adb devices


Check if your device is listed in output, then proceed

adb shell settings put global heads_up_notifications_enabled 0



reboot device and thats it!


Rooted devices


Using terminal


Install Terminal  for Android.
Open the application. Use the following commands:


su

(The indicator should change from "$" to "#"). Next enter

settings put global heads_up_notifications_enabled 0
Using heads app switcher app


One XDA developer has generously shared thier 50 lines of code embedded in this app to switch on/off Heads-Up notifications from quick settings for Android N
Root required. Reboot not required
Download here



Acknowledgements:


Official Nougat - turn off Peek Notifications?