How can God have always existed?

How has God always been here? If someone asked you ‘ Who created God?’, you would probably say ‘ No one did. He has always been there and always will’. The thing that I don’t understand is how is that possible?

“You are my witnesses,” declares the LORD,
“and my servant whom I have chosen,
so that you may know and believe me
and understand that I am He.
Before me no god was formed,
nor will there be one after me (Isaiah 43:10).

Well, in heaven which is where God is there is no time. God created time but just because He created time doesn't mean where He is (which is heaven), there is time.

So there is no time line, no time!

God bless.