Geez… what a box. And still I cannot figure out how to get a proper shell as Admin (got root.txt though). If anyone was able to get a shell as Admin/System, I’m glad to hear. Otherwise I’ll probably wait… 
Thanks a bunch @sckull for this one. It’s a 30 box that should be 45!
Edit: fortunately I’ve recalled that when you have root.txt you can unlock some protected writeups that you can find with google, and compare other approaches (in this case I’m actually learning properly this way). Definitely too difficult for my current level.