Investing in property in Qatar is a huge and unprotected risk due to the immaturity of the real estate industry as well as to the lack of transparency and adequate legislation to protect the consumer.
In a “normal country” you would be compensated for any delayed occurred. Please check the terms of your contract and if delays are addressed there, proceed accordingly with the assistance of an attorney. If there is no clause to protect you against delays, try to consult a local attorney to see if there is any way you can claim your compensation, after all the contract terms were not met and therefore damaged was inflicted on you by who ever you signed the Contract with.
Good luck to you, but please be aware of the risk you and some other innocent people put them selves into.