There are too many typos to list individually, so I will put the entire corrected text here with the corrections bolded. I am also not touching the grammar, since it's more or less a mess.
The Quelii system is located in the Ottega sector it is home to two planets and one bright yellow star. The two planets are Casit and Dathomir, they are both hot planets. Dathomir has no atmosphere while Casit has an atmosphere but it is toxic. There is not life in this system that is known other than the researchers that are here studying the ruins. The Ruins they study are of two very old human races. They both date back to days that predate the Old Republic by a long time. One on each of the different planets. Life here must have evolved much faster than elsewhere. Both races had huge planetary wars, and were very industrial.
On Dathomir the people managed to save the best and the brightest of their race and launch them into space before the atmosphere of their planet finally devolved, it is unknown what happened to these people, though some suspect the original settlers of Casit were these people. One would think that after a race had lost one planet, that they would put measures in place so that it would not happen again. That is the reasoning behind the opposition of this idea that both races where really one. Researchers work around the clock on both worlds to discover what really happened here, but much of both races have been destroyed through pillaging during the days of the Old Republic.
Other than these two dead planets there is nothing of value in this system most of the raw materials where striped away by the races that were destroyed here.