How can I delete files on my WD My Cloud drive from my Mac, if WD Apps are not working?

After upgrading the SSD on my iMac WD Sync and all the other WD Apps for Mac are not working anymore (see As my WD My Cloud drive is almost full I would love to delete most files on it. I mounted it as SMD Drive in the Mac Finder, which works fine. But when I try to delete folders, most of the time I get an error message, that certain files couldn’t be deleted, because they are in use, which can’t be true.

Any idea what I can do to batch delete a lot of folders from my Mac?

I managed to delete the files by login in via ssh on my Mycloud drive. From the terminal I could then delete all the files via a simple “rm” command. Now the files are deleted, but I have another problem: Although the files are deleted, the space on the cycloid drive was not freed, it’s still taken. If I look on the web dashboard half of the space is taken my “other” files… Is there a kind of trashcan or so in the drive, that I can delete? Or anything else I can do?