Is this legal to rent unfinished residential property?

My situation is the following: I supposed to move in into a property on the 15th of January. A new development and I am very excited. 3 days before moving in the agent contacts me and says the property is not ready. I told him I have nowhere to stay and asked for alternative for the time my flat gets completed. I got a spare room from actual landlord to stay in until he said I could take another room in the actual property above my flat and wait there until my flat is ready. My flat is still not ready, actually the whiole house is still under construction. Some of the flats are finished to 80% the corridor has no floor finish and the elevator is not working. The means of escape is not provided as the entrance door and also escape door is operated only by key lock right no. There is no telephone or internet connection and this is the reason for not properly functioning front door. There are no waste bins provided. My excitment of this new development has become to a frustration. The building has no registered postal adress. Can I legally request reduction to rent? Is the whole situation legal at all? I have not signed the contract yet but will have to in couple of days as I will be moving in into my almost finished flat. I appreciate any information that could help me to think clear right now.