Trade languages are common in the galactic network and while there may be a few, everyone on this ship finds that they happen to have one in common with one another.  It wouldn't be uncommon for ships crews to be organized with a careful enough eye to make sure that there's no one who doesn't know any of the languages.<br/><br/>Let's say that translator technology is difficult enough to manufacture (requiring knowledge of at least two languages on a fluent level and the engineering/coding know-how to create the device itself) that they're generally reserved for diplomatic missions or exceptions to the above where, perhaps, a galaxy-renowned doctor is contracted to be on a particular ship, but doesn't know any of the languages the crew speaks.<br/><br/>As for engine rooms and other essential equipment, your characters will find them curiously absent from the ship in their wanderings.  As far as they know, the rooms listed are the only ones on the ship (or at least, are the only ones they have direct access to).