Hi Ari777.
Your score on the Manhattan test is likely lower than you'd score on the real GMAT. Those tests are known to produce lower-than-normal scores. So, the 660 and 680 you scored on your recent official tests likely more accurately indicate where you stand at this point.
To get to your 730+ score goal, you can work on quant in two ways.
One way is to continue to strengthen weaker areas. To strengthen a weaker area, review the relevant concepts and strategies, do practice questions in that area UNTIMED until you're achieving high accuracy, and then work on answering questions in that area faster until you're answering them at test pace while maintaining high accuracy.
The other way is to reduce the number of careless errors you make and improve overall accuracy. For a detailed discussion of how to do that, see this post.
Improving Your Accuracy on the GMAT _________________