Verb conjugation of "costituire" in Italian

My mom and dad used to speak English when they wanted to say something I shouldn't understand. In this way I have learned English. I did not tell them till late, but I did understand every word they said.
Drinking coffee at night is supposed to be bad. Why? I have no idea. I believe the contrary is true. Coffee opens my veins and let's blood flow better and quicker. I therefore have nicer dreams, mainly from my last vacation in Italy.
These may be linguistic and cultural differences. There are indeed various regions throughout Spain and the word choice is not always the same. It is sometimes hard to understand people from other cities.