First of all what you need to realise is that your observation of the world is based on objects that a large and slow moving.
Also humans have limited perception of space and time
We just don't come equipped with the necessary "measuring equipment" to really observe the quantum and relativistic universe
Just like your ears cannot hear high frequency sounds, but a dog can.
when objects become really small they behave in ways that seem illogical. But various mathematical models and experimental observation can explain them. When you plug larger masses into these equations (like dividing 1 by a huge number approximates to zero) what happens is the equations reduce down to classical/Newtonian mechanics - hence proving there validity. So classical mechanics is hence proved to be a special case, but still useful as the equations are easier to work with
The universe that we know and understand and are able to sense as humans, is really just a small subset of reality
