The word consists of two syllables. The `a’ is pronounced like the `uy’ in `guy’ and `buy’; the `i’ that follows sounds like the `ee’ in `fees’, `bees’, and `sees’. The final `e’ is silent, and the stress is on the second syllable `iv’. This is just one of the ways of pronouncing the word.
When you say that someone is `naïve’, what you mean is that the person is very trusting. He is very inexperienced, and as a result, he doesn’t know very much about the ways of the world. He willingly believes everything that people tell him.
*Jai is naïve enough to believe that politicians are really interested in helping people.