Answer:
Adjusting/ entering a new culture, and the struggles of this.
Step-by-step explanation:
You see them comparing and contrasting their old life from their new, and even using the words "different culture". The choclate milk is just an example/symbol demonstrating this, and you can really see them trying to adjust "I wanted to open it.". But they clearly didn't know how. This is a struggle of the adjustment.
Hope this helps!