3. He speaks many languages
When he won the ATP Rome tournament, his trophy acceptance speech was in Italian. When he won his first Roland Garros Grand Slam, it was in French. Then for the Laureus Award, he started with Deutsch (German).
Those are three among other languages Djokovic speaks fluently, such as Serbian and English. It was not a simple Buon giorno, or Merci beaucoup, or Ich liebe dich. He speaks them fluently. He also speaks a little bit of Spanish.
How did he learn all of these languages?
Djokovic says that he loves languages. Wherever he goes, he would want to learn a little bit of the language, at least to have some casual conversation with the locals. So, he has been practicing them as an autodidact.
He picked up Deutsch as he lived there for tennis training. Some of his family lives in Italy. Now, he lives in Monaco, where most people speak French.