HAHA, You're mad!
You correctly stated everything even water in high enough amounts can reach toxic levels, yet you say adding extra fluoride is no big deal because it is a naturally found compound?
Why is adding fluoride past natural amounts a good idea when it as with everything else increases toxicity?
Come on... seriously? You are this fucking stupid?
I'll repeat what I wrote before – if the amount of fluoride present in water (either naturally or by supplementation) is at the recommended level then you will be dead by the toxicity of the water itself (regardless of the fluoride) long before you accumulate a clinically significant amount of fluoride in your body.
Let's play math and consider a worst-case scenario: the maximum recommended amount for fluoride is 1 milligram per liter of water. Let's assume that your water has twice that much. Let's also assume that all of it is sodium fluoride. Let's also assume that 1 gram of sodium fluoride will kill you – in reality you need about 10. Our simple equation is:
(2 milligrams of NaF per liter of water) * (1 gram per 1000 milligrams) * (x liters of water) = 1 gram of NaF
In other words, you'd need to drink 500 liters of water – that's over 132 gallons of water, or over 5 gallons an hour for 24 hours straight. Please remember that the human stomach can hold (on average) just over a gallon and the average human can excrete a maximum of a quarter gallon per hour under ideal circumstances.
It should be clear as day that short of eating a spoonful or two of NaF powder, consuming enough sodium fluoride is just not doable.
To address your other question, which seems to be "if water is toxic why add more toxic stuff to it?" well... the answer to that is that scientists who know this stuff much better than you have determined the benefits of fluoridating water by helping improve the dental health of the population at large outweigh the realloy small risks.
If you disagree with their assessment – and you can – buy a water pitcher and filter your water. Or don't drink water at all. But don't pretend that your disagreement has a basis in science. It doesn't.