The 60-Day GMAT Study Guide

I am on day 14.I study for 2 hours and only do the OG 13th problems, not the quant 2nd in the additional work section. Going through the practice OG problems I am only getting about 40-50% right, the others I get wrong because I do not know how to solve for, but I do review the problems I get wrong and figure out how to solve for the answers. Majority of problems I am getting wrong in the data sufficiency. On day 22 there is another practice exam. If my score has not improved closer to where I want it to be should I repeat the days 1-21 and do the additional problems in the quant 2nd ed too or should I go on to day 23 review the math section later?

I think my Quant score is 17 or 19 when I took the practice , I want to improve it to Q30+. I need a 500+ score to get into the program in my area.