got root.
summary of everything that have already been said before:
Foothold: read the page, find some interesting things & google this “interesting thing”. Once you think you find it, be patient and test everything you found.
User : I suggest you get a proper shell, then everything is in front of you in plain sight. A command that you should always be running will get you to user’s flag.
Root: There was a box with a very similar flaw couple of months ago. Use pspy to get the root’s flag (or shell or anything, really). Read carefully the output and focus on permissions.
Ping me if you are stuck. However do not ping me without a description of what you have done already. The initial foothold might take you a while, but once you think about what is author telling you, you’ll get in easily.
Good luck