I would like to know how to correctly write the following sentences.
1. I don't know what are you doing. or I don't know what you are doing.
2. I don't know what is happen. or I don't know what happen is.
3. I don't know what is going on. or I don't know what going on is.
Remember that you reverse the person/verb order if it's a question. If it's a statement, you don't.
I don't know what you are doing.
What are you doing?
I don't know where the book is.
Where is the book?
He wants to know who the author is.
Who is the author?
Note that this doesn't apply when there is no "person" involved!
He doesn't know what is happening.
What is happening?