The message thing is kind of... silly. You have to click another tab on the message site and then go back to the tab with the messages. Happens most of the times with the tickets.
Don't trade with the cat merchant, at least not until you know the value of your cards. He makes most of the time deals that aren't that great but sometimes he can give you true valuable cards you want at any time. That's how I got my Angel Orperia card.
On terms of crashs: That migth just be your ohone running out of memory. of course this is to soem extend the fault of the game because it seems not be fully optimised. Closing other apps before might help.