Camera showing black screen. there is a shuuter button but not working

I understand you are saying you already tried a soft reset?

If not try that first, hold the volume down and power buttons at the same time for at least 10 seconds, until the phone restarts.

Next try to clear the camera application data:
Settings >Apps >Camera >Storage >Clear Data

You can check for any available updates, and install them, perform a reset again afterward if the problem remains. You can also try restarting in safe mode; if the device works in safe mode properly uninstall any recently installed app that uses the camera, you have a software conflict. this video explains how to use safe mode on your davice

If all that fails dial #0# into your telephone keypad and select 'Front Camera' or whichever is problematic from series of options. If the error occurs during this test contact Samsung Support.