All is ok here and Kahramaa is a govt. owned organization with 90% ARABIC speaking people. Salary is all you can negotiate and it is up to you.

Life of Qatar, well, its alright but if you are comming from UAE, you may find it boring. Not much to do here, not much at all.

Also, keep in mind that overall in Qatar, NOC issue is on high but since Kahramaa is govt. owned, i really cant comment if they will let you have it.

About yout passport, most of the govt. agencies and govt. owned organizations dont keep passports of the employees but having your passport with you is no good since you need an exit and that is provided by your employer.