OK, so I messed around with PulseAudio and purged all of it. Now my regular sound settings do not work anymore. neither can I turn up and down the volume with the respective keys, nor do the sound settings show any devices (neither input nor output). The sound symbol does not show in the menu bar anymore either. I can hear sound though.
I guess I accidentally uninstalled a package that is needed. Does anybody know which packages I have to reinstall?