Pulseaudio Config works only after manually killing it

I’ve tried every tutorial under the sun to set my standard audio device. Yet after a restart it never works, only if i restart Pulseaudio, via “pulseaudio -k”, the config file seems to get into action.
The only thing i changed to the Config is append
set-default-sink alsa_output.usb-SteelSeries_SteelSeries_Arctis_7-00.stereo-game

Since I am a complete beginner in Linux, any advice would be appreciated !

Did I forget something in my question?