It is indeed a very good salary and if bonus comes in, you will be going over the moon.
As a person who is single, I guess your total expenses for each month will be around QR 9000 per month if you decide to live on a single-occupancy basis. However, should you decide to share your accommodation or someone shares his accommodation with you, your expenses will go down by say QR 2000.
At the end of the month, your expenses depend solely on your life-style. If you drink or visit bars or socialize much, the expenses will surely add up.