Arguments against existence of God.

[Cherub786]

Scientists say there is an explanation for everything, even if we haven't found it yet. Mathematics is a mental construct.
Scientists don't believe the cosmos is eternal or without beginning, most of them anyways.

I don't know where you are getting your information; even if true, the majority to most scientists are atheistic:

A 1998 survey based on a self-selected sample of biological and physical scientists of the National Academy of Sciences in the United States found that 7% believed in the existence of God, 72.2% did not, and 20.8% were agnostic or had doubts.[49] Eugenie Scott argued that there are methodological issues in the study, including ambiguity in the questions. A study on leading scientists in the US, with clearer wording and allowing for a broader concept of "god", concluded that 40% of prominent scientists believe in god.[50]

Wikipedia -- Demographics of atheism: Geographic distribution

Ditto for most philosophers:

The Largest-Ever Survey of Philosophers: What Do They Believe?

It's immaterial whether majority of scientists are atheists or not. The point is that majority of cosmologists and physicists acknowledge the truth that the universe is not eternal, and they generally agree that they have no solid explanation for how and why the universe came about.

They say that the beginning of the universe is a "singularity". Now it is all theoretical, based on mathematical formulas and so many assumptions.

Even these atheist scientists are forced to admit that the questions about the nature of the cosmos and how it came into being naturally lead to belief in God, as Dawkins said:

I think that when you consider the beauty of the world and you wonder how it came to be what it is, you are naturally overwhelmedwith a feeling of awe, a feeling of admiration and you almost feel a desire to worship something. I feel this, I recognise that other scientists such as Carl Sagan feel this, Einstein felt it. We, all of us, share a kind of religious reverence for the beauties of the universe, for the complexity of life. For the sheer magnitude of the cosmos, the sheer magnitude of geological time. And it's tempting to translate that feeling of awe and worship into a desire to worship some particular thing, a person, an agent. You want to attribute it to a maker, to a creator.