Maybe there could be a lesson around the verb 어렵다.
As I understand it, if you invite or ask a person from Korea something, they would not be so direct as to say "No, I can't".
They might say "Well, I am supposed to do this other thing at about the same time, so it would be difficult..."
If this is right, then that would be a good verb to know. I'm new but I don't think there's been a lesson on politely saying "I can't"
고마와요