How to stop Automatically kill apps and notification

[AC Question]

I have recently purchased a new Nubia n1 phone whenever I try to drop down my notification bar neither it gets down completely nor allow me to see any of my notification it automatically clear all the notifications, even when I long press my back key to see what application are running in background it closes all the application. Kindly tell what i need to do to find the solution to my problem.

 

[B. Diddy]

Welcome to Android Central! Does this happen in Safe Mode as well? The steps for the Z9 presumably work for the N1: How to turn on safe mode on Zte Nubia Z9 Mini