In addition to the other good answers ...think about something pretty straightforward like gravity. We all agree gravity exists.
And yet, we don't actually *know* how gravity works. Isaac Newton made a pretty good first attempt at describing gravity, and his theory got great support when it successfully predicted the location of Neptune, based on the orbit of Uranus. But problems still emerged; Newton's theory could not account for variations in the orbit of Mercury. As part of his Theory of General Relativity, Albert Einstein was able to explain perturbations in Mercury's orbit by treating gravity as a curvature in spacetime, rather than as a force. Okay, so now we know how gravity works ... except that General Relativity and Quantum Physics can't be made to agree on how gravity works. They both have theoretical and experimental support and appear to be "true" but cannot be reconciled. In Quantum physics, gravity is sometimes viewed as the actions of hypothetical particles called gravitons. Except that gravitons have never been observed, and won't work properly over very short distances (less than the Planck length). There are also experimental observations in the real world which contradict any of our understandings of gravity - for example the "flyby anomaly" of spacecraft, or the existence of super-massive hydrogen clouds in space.
Now someone could come along and say "Gravity is a myth; none of the scientific explanations work; things fall down because of the invisible hand of God pushing them down".
What would be the best response to a claim like that? Should we say "Yes you're right; after 300 years of trying we still can't explain gravity so we should accept that it is the invisible hand of God making stuff fall down"? Or should we say "Our knowledge of gravity is imperfect but getting better and better all the time; and even if there are gaps in our knowledge we've still used the theory of gravity to land astronauts on the Moon, put GPS satellites into space, land exploratory vehicles on Mars, and calculate the height of forthcoming ocean tides. In time, with more research we will work out the gaps in our understanding; so we're not quite ready to give up and adopt the "Invisible Hand" theory of the anti-Gravitationists"?
Today, we don't know exactly how Life arose from non-living matter. However, we now know a lot more about how Life works than we did 100, 50 or even 15 years ago. There are some promising hypotheses about the emergence of Life, and it is possible - even likely - that within another 50 or 100 years, we will know how Life began.
Meanwhile, it's really throwing the baby out with the bathwater, to reject the Big Bang and Evolution of Life, just because we haven't quite solved the issue of abiogenesis yet. The evidence for the Big Bang is overwhelming. The evidence for Evolution is also overwhelming. They cannot be dismissed as "completely out of the question", because of a guess that abiogenesis is impossible. If you can account for the same observational data with a different or better theory - that's great! But you can't reject the Big Bang and Evolution, including the observed data, just to replace them with an explanation based on mysticism.
For experiments and scientific evidence supporting abiogenesis, try the links below.
As an afterthought ... there's very strong evidence to show the Universe is around 13.7 billion years old. There's even stronger evidence to show that the Earth is 4.55 billion years old. We have found remains of living organisms on Earth stretching back around 3.5 billion years. There's enough evidence now that these can be accepted as "confirmed". If not for the Big Bang, and the (much, much later) formation of the Solar Earth and Earth, and the first appearance of Life on earth, then how *did* these things happen? And what was going on with Life, during that 3.499998 billion years on Earth, since Life first appeared but before humans appeared?
Hope it helps.