Android 5.0.2 hide navigation bar on Lenovo Tab 2 A8-50 I have issues when run shell commands that require root privilege on Lenovo Tab 2 A8-50 (rooted)

1- I'm trying to hide the navigation bar on using adb shell command


I have to restart the device to get the effect but I get a black screen after restarting so I have to enable systemui to make the device run normally again "pm enable com.android.systemui".

2- Also shell command for screen capture get the "device launching image only" not the device screen "su -c /system/bin/screencap -p /sdcard/img.png"
The same commands run properly on different devices. Is there any kind of protection on this device that prevent shell commands run normally? What do I have to do?
The first thing you do literally disables SystemUI, including lock screen, status bar and navigation bar, hence you get black screen on reboot. Whoever told you to do that... deal with him.

Simply use the old build.prop trick (qemu.hw.mainkeys=1) or apps like GMD Hide Soft Keys.