Hi, and welcome to the community!
If you go to your account overview, you can sign out everywhere so the user cannot log back in. You can also check your email is correct.
If there are changes to playlists that you can't revert, submit an online contact form; someone at Spotify can sort this out for you.
Once you get an automated reply; make sure to reply to it directly (even if it's from a no reply); and it will be sent to the Spotify staff.
Thank you for the swift reply! I logged out as per your instructions 😉
E-mail is the right one, though not sure if I should change it now…
Also I was able to change the password twice but I don't know how helpful that can be.
I don't see anybody streaming music now, but before it stopped a playlist (with no songs) named "want to communicate?" "magically" appeared on my music… I think I'm in the matrix 😕
Hey there you, Yeah, you! 😁 Welcome - we're glad you joined the Spotify Community! While you here, let's have a fun game…