The cosmological argument for god (commonly known as the 1st cause argument) claims the following premises:

1.All things in existence have a cause.
2. God is uncasued. (or phrased as a minor premise "No God has a cause"

It logically follows that:
No God exists.

No logical flaw can be found in this argument, therefore, given the validity of the 2 premises, there can be no God.
To then assert is a god would be to claim that one or both premises of this argument is false.
However, in doing so, this demonstrates that the first cause argument for God is unsound(based on a false premise.)

If one then claims God has a cause, then God was not needed to set things in motion, meaning god was not the first cause or possibly that there was no first cause. Therefore a god is not required for existence.

Otherwise, one must claim that not all things in existence have a cause. the major premise of the argument becomes "Some things in exaistance have a cause." Again, meaning the first cause was not necessarily God. An assertion otherwise bears the burden of proof.