How to debunk the first cause argument without trying too hard

[Esquilax]

It works to everything that is in state of change from one state to another.

... Within the universe. How can you possibly determine how it works in other states of existence, like that of the pre-big bang universe? Actual scientists throw their hands up at answering that question within the framework of our current capabilities, they say we'll require a whole new set of physics, an entire new lexicon, before we can even begin discussing it, and yet you're going to tell me that you just know?

When I tell you that beyond certain boundaries we're discussing things so far outside of our frame of reference that even the language we use to talk about it is unsuitable, tainted as it is by the assumptions and processes of the temporal reality that formed it, I'm not joking. Quit trying to force your intuitive sense that everything works like the world you've been exposed to does into the conversation; it's simply not applicable.