Notebook Webcam not working in Gnome

Dear all,

if somebody says, there are already some posts with the same topic…
Yes there are but these posts couldn’t help me. Maybe because I am a god damn noob.

I tried cheese to check if my webcam is working and the app says, that there is no device.

So i tried some hints from other posts and also found out that the /dev/video0 cannot be open:

~ >>> v4l2-ctl --list-devices                                                  
Cannot open device /dev/video0, exiting.

I hope you can help me!