Human opening
The topic of this debate is "Does God exist?". There are three ways to answer this question. Answering yes would make you a theist, answering I don't know or I'm not sure would make you agnostic, and answering no would make you an atheist. In this debate, my burden is to prove that God exists. My opponent's burden, as they say they are an atheist, is to show that God doesn't exist. We can define God as a spaceless, immaterial, supernatural, and uncaused being who created the Universe. I will defend two main contentions in this opening. The first one is that there are no good arguments for atheism. Instead of attacking strawman on this point, I will wait for my opponent's arguments to explain why God doesn't exist. I will instead move to my second contention, which is that there is evidence for God's existence. I will show this first through the contingency argument. First, everything that exists has an explanation for it's existence. For example, a wooden chair might exist because a carpenter chose to make it. A city might exist because multiple people chose to set up establishments there. The explanation for something could be an external cause as in those examples, or have an explanation out of the necessity of it's own nature. Second, because everything as an explanation for it's existence, that the universe must have an explanation or cause for it's existence. This cause must be spaceless, because it brought space into existence, it must be immaterial because material objects cannot exist without space, it must be supernatural, because natural means it is of the universe and this cause must be outside the universe, it must be powerful because it is powerful enough to create and sustain the entire cosmos, and it must be uncaused. Therefore, this explanation is God.
First rebuttal
You're smuggling in your conclusion before the argument even starts. You define "God" as precisely what you need to conclude, then act surprised when the contingency argument delivers it. That's circular reasoning dressed up as logic.
Here's the real problem: you claim everything needs an explanation, then exempt God from that rule. Why? "Uncaused being" doesn't solve the problem, it just relocates it. If God can exist without a cause, why can't the universe? You've given no principled reason for the asymmetry.
Why does "necessary existence" apply to your God but not to physical reality itself?