Why do humans have organs in sets of 2s and 1s.
Why are some organs (1) - The head, nose, mouth, heart, stomach, etc …
Why are other organs (2) - Eyes, Ears, Nostrils, Lungs, Kidneys, etc …
Is it related to the functions ? What is common between the 1s and the 2s ?
Hope this is not MUCH as my first question 
And some are in fours (limbs, which have fairly similar structure whether fore or hind), and some are in 20s (fingers and toes).
It’s a lot easier to make body parts that are all variations on a single basic plan than it is to make body parts which are fundamentally different from each other. Some things we only really have use for one of them, and so we have to have a special design just for that part, but some things, for various reasons, it’s useful to have multiples. Of course, even the “single” parts are often composed of multiple sub-parts which are similar to each other. Heck, we have one body, which is made up of two nearly-identical symmetrical halves. That symmetry, in turn, is the reason why the things we have multiples of, we mostly have an even number.
This isn’t philosophy, it’s biology. Specifically, evolutionary development.
Ultimately, it’s because we evolved from worms, so we have a rough bilateral symmetry: You can split us down our long axis, from head to crotch, and end up with two approximately similar pieces. In fact, we’re built around a digestive tract that’s still pretty much a long worm, from the esophagus to a bulge for the stomach to a long, winding small intestine, to a simpler loop of large intestine to a smaller bulge right near the anus.
Anyway, this means that what’s on one side is likely to be replicated on the other. Hence we have two lungs, two eyes, two ears, two arms, two legs, two kidneys, and various other duplicates.
Compare us to starfish, which have a radial symmetry: They’re the product of a different evolutionary path.