Very delicious or not very delicious?

My students, my latest students, and my favorite group so far, are Korean, French, Brazilian, Turkish, Swiss and Italian.
They all get along pretty well, and like to pick on each other. Sometimes I can't help myself, and laugh at them too.
For instance, my Turkish student, Ali, would ask me to check his homework and would ask, "Teacher, true?" Instead of "Is this correct?" He was also famous for saying, "I wear slippers in home, MAYBE?" Meaning, "Can I wear slippers at home?" He was also known for saying, "Thank you very much" after every question I answered.
My French student, Mathieu, who is young and wants to party mostly, always says either "yeah, yeah, yeah" or "no, no, no" with his very French accent and sounding bored the whole time.
My Brazilian student, Jose, would always announce to the class "No good" when he would miss a lot of the questions for homework. Or would bluntly tell me, "No understand" when he just didn't get it.
But the best is what my Korean students say. They have two categories of American food, "Very delicious" or "Not very delicious." I sat with them in a cafe and laughed when two girls passed a crab salad wrap back and forth, one who did not like the sandwich and one who was willing to try it. "Delicious or not very delicious?" the one asked. "Not very delicious," said the other while she made a face that said more than "not very delicious." My other student tried a bite of the wrap and confirmed, "Not very delicious."