From my understanding `dark matter` is an explanation for what we expected and what we see regarding the mass of the universe? It's a bit like exploding an app

From my understanding `dark matter` is an explanation for what we expected and what we see regarding the mass of the universe? It's a bit like exploding an apple and measuring all the bits that fly of and missing some bits. Whilst we do not know what the apple looked like initially, we are from our measurements, trying to reconstruct that apple. How convinced are we that their is dark matter and not a case of how we have measured things so far. Hence, differences in results based upon how we measure are evident, whilst many are close to the same, they just don't exactly match up - hence - dark matter theory. How likely is it that dark matter as we know it - does exist?