can i have a refund on my car?is it repairable?

i bought a car on 11.1.11,two days later was overhaeting,took it back into car dealer and found there was a leak,was told to keep water level topped up,which i did.then came a burning smell from the engine,took i back in and some sort of liquid was put in to find and seal the leak.since this was put in(2 days ago)engine warning light has come on,car is juddering very badly and theres no acceleration,very sluggish.