What are Al Pacino and other people talking about when Al Pacino said "It's longer? Longer like what? Like my dick is longer?" and the other person says "No no no, we are not talking about a Volkswagen." What does that mean?
In that scene, they are comparing the Lincoln, Cadillac, and Mercedes automobiles.
One guy says "I'll tell you one thing, my friend. Undisputable. The Lincoln is longer." He is talking about the length of the Lincoln Town Car - he is saying it is longer (has more length) than the other cars.
When Al Pacino says "It's longer? Longer like what? Longer like my dick is longer?", he isn't sure what the other guy means when he says the Lincoln is longer. So he throws in a comment about his penis.
Then the other guy insults Al Pacino's penis size by saying "No, no, no. We're not talking about a Volkswagen." A Volkswagen is much smaller than the Lincoln Town Car.