There are some spam issues in the comments, so I had to disable comment editing for a short time. It'll be back once the spam bots are gone. FYI... they leave a comment with "great" and then edit in the spam stuff later, to get around the filter.
(In daily life, "auf" is much more common for doors and stores but "auf" doesn't work for figurative things like an open mind. That's what you'll need "offen" for.)