"as all of you know that when you sign a rental cotract, the contract is in favor of landload[sic] and in arabic"... I don't know that.

Sorry, but Arabic is the language of the land. If you were in Germany, France, Russia, China, ... you wouldn't be complaining about the language like this. You should have gotten it translated (at your own expense) before signing. And It's never in favor of the landlord, it's usually a compromise between both parties. How do you know it's "in favor of the landlord" if you didn't read it???

You don't need NOC to "leave qatar for goods[sic]".

You would be deceiving your landlord, you don't lose anything by informing them.