XFCE Shortcut problems

After installing XFCE i had multiple Problems with my hotkeys. 
 I installed XFCE on Ubuntu with sudo apt-get install xubuntu-desktop 
 Every step can be added at Open Menu -> Settings -> Keyboard -> Tab Application Shortcuts. 
 Media Keys 
 Next Track 
 Command:
 dbus-send --print-reply --dest=org.mpris.MediaPlayer2.spotify /org/mpris/MediaPlayer2 org.mpris.MediaPlayer2.Player.Next 
Key: 
Press the Next Track Media key. 
 Previous Track 
 Command:
 dbus-send --print-reply --dest=org.mpris.MediaPlayer2.spotify /org/mpris/MediaPlayer2 org.mpris.MediaPlayer2.Player.Previous 
Key: 
Press the Next Track Media key. 
 Play/Pause Track 
 Command:
 dbus-send --print-reply --dest=org.mpris.MediaPlayer2.spotify /org/mpris/MediaPlayer2 org.mpris.MediaPlayer2.Player.PlayPause 
Key: 
Press the Play/Pause Media key. 
 Stop Track 
 Command:
 dbus-send --print-reply --dest=org.mpris.MediaPlayer2.spotify /org/mpris/MediaPlayer2 org.mpris.MediaPlayer2.Player.Stop 
Key: 
Press the Stop Media key. 
 Source : man42.net Blogpost 
 Lockscreen and WhiskerMenu 
 Lockscreen 
 Command: xflock4 
Key: 
Press the Super + L Combo for Windows Like Lock 
 WhiskerMenu open on Super 
 Command: xfce4-popup-whiskermenu 
Key: 
Press the Super Key 
 Note: Super L will be displayed as Key, works still as intended.