Disk space is running out

I´m running NC 19.06 and all useres have a used space of app. 30GB.
Under Systems the used disk space is about 180GB.
My settings for deleted files are “180days” and in the trash bin is nothing older than 3 months.
what can I do to get back more free disk space? It seems that something went wrong.
I have not deleted (as far as I remember) any user
I think I was handling a lot of video files and from this time I have massive use of Disk space…
But those files are deleted since a long time.
I just have calculated: app. 30Gb are used (looking to the user overview). 33Gb are somewhare and 177Gb are free (looking to the used HDD overview)…
what are the 33Gb? How can I delete them?

there is also versioning. Normally it should delete the files once the space is needed. With the occ command you can also trigger a manual deletion: https://docs.nextcloud.com/server/20/admin_manual/configuration_server/occ_command.html#versions

Thanks for that Link.
I tried the clean up command and it worked - but I do not get much more space back from my HDD.
Is there anything else I can do?
In between I updated to NC20.0.4 and it runs without any “errors or Informations”
I deleted the trash - that gave me additional 3Gb.
I still have a leack of 30Gb. Where do they come from? Maybe they are old files - shared but deleted? Could it be that they are still somewhere in the system? If so - how can I find and delete them?

Take a look at the du command in Linux, it can show you the size of folders…, e.g. size of all subfolders in the current directory du --max-depth=1 -h.