Hi Oda,
From a statistical-standpoint, the type of improvement that you are looking for would likely require that you study for another 1.5 - 2 months. Raising a 470 to a 550 in just 3 weeks is possible, but you will have to make some significant changes to how you work through the Quant section. Thankfully, the GMAT is a consistent, predictable Exam, so you CAN train to score at a higher level.
With a Score Goal of 550+, you do NOT need to correctly answer ANY questions on the GMAT that you think are too hard or too weird, but you do have to keep the little mistakes to a minimum. As such, you should look to quickly 'dump' any questions that you think are too difficult - then you will have more time to spend on all of the other 'gettable' questions. Before I can offer you any additional advice for your studies, it would help if you could provide a bit more information on how you've been studying and your goals:
1) How long have you studied? How many hours do you typically study each week?
2) What study materials have you used so far?
3) On what dates did you take EACH of your CATs/mocks and how did you score on EACH (including the Quant and Verbal Scaled Scores for EACH)?
4) What application deadlines are you currently facing?
GMAT assassins aren't born, they're made,
Rich