Sagt ein Narr nur ein einziges Wort, weiß der Weise schon, was Sache ist.

Italian Translation

A buon intenditore poche parole.

Not the correct translation. The right one is
Se uno sciocco dice solo una singolo parola, il saggio sa già cosa sta succedendo.
or in English:
If a fool only says a single word, the wise man already knows what is going on.