YES / NO QUESTIONS BE (AM, IS, ARE)

Subject and verb change their position in statement and question.

STATEMENT: You are from Germany

QUESTIONS: Are you from Germany

Am	I	right?
Is	he	here?
Is	she	a nurse?
Is	it	second-hand?
Are	we	wrong?
Are	you	Alan Parker?
Are	they	American?

We always use the short answer, not only "Yes" or "No".

NOTE:
If the answer is "Yes", we always use the long form. 
Example: Yes, I am.

If the answer is "No", we either use the long or the contracted form (short form).
Example: No, I am not - No, I'm not.


http://www.englisch-hilfen.de/en/grammar/frage1.htm