[John used to have a good life and successful career, when an accident made it impossible for him to return to his professional field. After a long period of troubles and failing attempts to find other job, his brother who just bought a car and was pleased by the ambience at the dealership tells him to try to get a job there. John has no idea of this business and not a hint of desire to work in it, but in despair decides to follow the advice. At the dealership, they first take him for a rich potential buyer, but then he says to the owner that he is actually interested in work]
"Work? What kind of work?"
"Well, my brother said this is a place that I might be able to sell some cars."
An internal cringe as I show off my detective skills.
"Your brother? Who's your brother?"
First, I don't understand who's having a cringe, John or the boss?
Second, what does "show off" mean here, and what it has to do with "detective skills"?
And finally, I can't understand the logic and the structure of the sentence. :((
Thanks for any help :)