Are You Sleeping?

An ex-student of mine sent me a message and asked me a question:

Which is right: DO YOU UNDERSTAND? or ARE YOU UNDERSTAND?

So, I told her the former is correct. As far as I know, we cannot use: Are you understand?

Are you sleeping? I still remember that line from the song my English language teacher taught me way back in Standard One Yellow in 1969 in Kangar English School (presently known as Sekolah Kebangsaan Seri Indera).

Then this student told me that, her friend used :"Do you understand" and her LECTURER said she was wrong and she should use : "Are you understand?"

Lecturer, ARE YOU OKAY???

OMG...