Existem três classes de pessoas que são infelizes: as que não sabem e não perguntam, as que sabem e não ensinam e as que ensinam e não fazem.

[theogarver]

English Translation

There are three types of people who are unlucky: those who don’t know but don’t ask, those who know but don’t teach, and those who teach but don’t act.

The first part of this statement is translated wrong as it is talking about types of people that are unhappy not about people who are unlucky. Existem três classes de pessoas que são infelizes = There are three types of people that are unhappy.