Please recommend basic expressions for communicating with Korean children.

How can I start communicating with Korean children? I work at a daycare in New Zealand, and there is a 4-year-old child of Korean nationality. This child does not use English at all, so it seems difficult for him to interact with other children or teachers. He mostly spends time alone, but he tries to interact with me relatively often. I want to understand what the child is saying and learn basic Korean expressions for communication. Is there a good way to start in this situation or any recommended resources? It would be very helpful to have materials or tips for learning basic Korean expressions, or if someone could share their experience in a similar situation.