If I'm in a debate with an atheist and then it comes to the point when he says "Then who created God?", how should my response or answer be?
In the name of God, the Most Gracious, the Most Merciful.
Atheists tend to ask this question to Muslims. "Who created God"?
God is the first, with no beginning, and the last, but with no ending. So the answer is that God was never created in the first place. He was there. That's it. Here's a video that will explain this: https://www.youtube.com/watch?v=-zVpw2-OD4M
Fully accepting the oneness of God is to accept that He is distinct from everything else. It would not suit God’s majesty and glory to associate the limited attributes of His creation to Him because He is not restricted in any way, while His creation is. He is the First with no beginning and the Last with no end. Everything in the universe was created by His will. He is not confined by space or time and He is the only One who is in control and provides for His creation.
That site will also help you on this regard, and how to talk to atheists in general.
I really hope this helps, and Allah knows best.
Peace be unto you.
Not that we can define God, but we know some of its attributes.
I think what you should do first is define what God is. when we say الله الصمد it means God doesn't need ANYTHING. ( don't read the verse to him but convey the message :D )
Whatever that is in need is created and therefore weak. There is only 1 entity in this world that is not in need and that is Allah.
Having that said. Depending on your situation. I recommend never ever engage in a discussion when one is not asking but rather making statements. Did this person come to asking about God or did you go to him assert your ideology?
If he comes to you then give him all you got. The moment you see him saying nonsense then that's the moment where you stop the discussion and not proceed.
In addition don't make statements. Ask him questions. Don't say There is a God. Ask him how do you think this universe was created. Keep asking questions until you see either his fitra (فطره) comes out, or you see him conceal کفر his fitra.