You bought your apartment a year ago, at what you say was a high price, signing a contract you say was in favour of the developer. Why? Who forced you to do that? Now you want to sue them, before the completion date, because you have changed your mind and haven't been able to sell. It sounds like you were very naive and made an investment you couldn't really afford, hoping to turn a quick profit. Buying 'off plan' anywhere in the world, you have to factor in some possible delay in handover. Have you spoken to the developer about your situation and about the revised completion date?