How can I have meaningful interactions with locals in Italy if I don’t speak the language fluently?

What is the meaning of "I am watching you" sign? I'm a girl, a senior male coworker at work does that to me from a distance and then smiles. How do I interpret this? Can someone make me understand this?
What are the reasons that make it difficult for people to adjust in situations?
Is it common for introverts to prefer reading and listening to music over other activities, and why might that be?