SamTweak

Set a few System Settings not available in Standard settings...
!!YOU DONT NEED ROOT BUT YOU HAVE TO GRANT PERMISSION VIA ADB SHELL !!

because of API-Level change google dont let me update the App :( new Version is here ->
https://play.google.com/store/apps/details?id=org.inteks.samtweak2

pls check https://forum.xda-developers.com/galaxy-s9-plus/themes/app-volumewarning-reverseprotrait-t3778873/

you need a working adb shell. the app creates a windows batchfile to grant the needed permissions. (thisPC->Phone->_samtweaks->GrantPermissions.bat)

once permission granted the app can enable reverse protrait oriantation ( i.e. needed if you like to charge you phone in cars cup holder with usb port on top)

disable the Max Volume Warning (if checked it come up once and then never again)

disable the Max Brightness Warning

and set Navbar Color to Black...