Why too much oxygen is harmful

Oxygen is very necessary for our life to continue, this is the gas on which all creatures depend to live, without oxygen we would die. It is really important but why too much oxygen is harmful? There is 21% oxygen in the Earth's atmosphere and all creatures depend on it for the continuation of their biological processes, but too much oxygen is harmful to the point causing disasters and kill us! One of the most important properties of oxygen in chemistry is that it does not ignite, but rather helps to ignite, this means a lot of oxygen causes massive fires, especially since the percentage of carbon dioxide that is responsible for extinguishing fires is very small compared to the oxygen. Not only this increased oxygen concentration causes diseases of the central nervous system, damages the lungs, shortness of breath, and eye diseases such as damage to the retina. Exposure to these symptoms is very low probability because the percentage of oxygen in nature is moderate, but there ar