No Stupid Questions

The question is a bit like "If I spend all my money, is it truely gone forever or did it just return to the global financial streams?"

Like with the money, water exists in very different states of usefulness. Sea water, for example, is incredibly abundant, but using it requires desalination, which requires enormous amounts of energy.

Ground water is really useful, because it's where you need it and it's usually pretty clean.

Rain clouds mostly pull their water from the sea. Hence using water e.g. in agriculture will not increase the amount of rain by any significant amount.

Ground water replenishment thus doesn't depend on the amount of ground water spent for e.g. lawns. Similar as your wages usually don't depend on how much money you spend on a holliday.

So if you waste ground water, it's mostly just gone, while you wait for rain to refill it. Sadly, in most regions that happens far slower than people are spending their precious water resources on useless nonsense like a green lawn.

Depends. Sometimes the water gets dirty and needs to be treated, sometimes it evaporates and needs to rain, sometimes it could be reused as is

In very rare cases (nuclear fusion) the water is destroyed into its primitive elements

You can't destroy it and it doesn't go anywhere. It just gets moved around and used for different things at different times.

Water lawn > Grass uses water to grow more grass > humans mow lawn > grass clippings dry out > water returns to atmosphere

Water is a bit more complicated than ordinary ressources, watershed are mostly local and it's hard to transport water over large distances. To make-it simple, saving water in Scotland won't bring more water to the Sahara.

All the water we use comes from rain (snow), and it would either go to the ground where it could be pumped, or join stream them rivers and flow downstream. A part of the water you use upstream will evaporate, and therefore won't flow downstream, which is the cause of big geopolitical conflict, especially in dry regions. This water will still evaporate and at a point fall back on the ground as rain, but you don't really control where (and when) the rain falls, moreover, with global warming, a hot atmosphere can store water than a cold one, leading to "less rain".

Another issue is ground pollution. If you keep the ground clean, you can pump water, people have stuff to drink, farmer can water their crop and so on, but if there is any pollution you might have non drink water in the ground or even contaminate the plant you water with it, meaning that water is lost... forever

While the water most likely returns to the cycle, in many places replenishing the aquifer can actually take years, even decades. In those places using too much water means the aquifer keeps depleting and causes a bunch of other problems such as salt water intrusion.