If you guys using a laptop you need to run the game with your dedicated graphic card (Nvidia or AMD) not with onboard card. Otherwise the game crashes.(at least for me)Right-click the application title and select Run with graphics processor.
I'm assuming you are asking about the dungeon and it's use and you also don't say if you've found it or not, or whether you're looking for the hidden card locations etc, as your reply is a little vague.
Hidden cards are an added extra, no actual advantage added is gained when playing the game.
[Call them bonus images to peruse at your leisure]
But you'd be better off asking, if you get stuck in the game, in the Walkthrough-FAQ thread here
You must be registered to see the links
But, to save little time for you this time... as I'm assuming you've not found the dungeon?
There are also hidden cards at his place of work, it's been a while since I looked for those but if I recall, one is in the main office and two others are in his actual office. Hidden cards hints/locations are also listed in the added link above. Use the search thread option to help you look for what you want.