Hi michdur07,
I’m glad you reached out, and I’m happy to help get you on the right track! Since you have been studying quant for the last two months and your latest quant score is a 24, you might consider taking some more time to first master the fundamental concepts of GMAT quant prior to completing any more random problem sets or studying more advanced topics.
So, for example, you might start with basic fraction operations (addition, subtraction, multiplication, and division), manipulation of basic algebraic equations, solving quadratic equations, basics of data sufficiency, etc. Once you master those basic concepts, you will find it much easier to learn more advanced GMAT quant topics.
Furthermore, when studying GMAT quant, since there is so much content to learn, you may find it helpful to take an approach that allows you to learn one topic at a time and follow up your learning with specific practice. In other words, you want to master one topic before you move to the next.
For example, if you are reviewing percents, you want to cover as much as possible about percents: percent less than, percent greater than, variable percents, and percent change. Then you will want to do many practice problems on percents (50 or more). The results of that practice will help you determine how well you have mastered that topic.
Follow a similar routine for verbal. When learning about critical reasoning, for example, learn about all aspects of critical reasoning (strengthen and weaken the conclusion, resolve the paradox, find the conclusion, must be true, etc.). Follow up your learning with focused critical reasoning practice, so you can determine your specific weaknesses within that topic. You should do the same for sentence correction and reading comprehension.
If you find that are you unable to fully learn GMAT quant and verbal with your current materials, you may consider using some additional resources.
Also, I understand that you are trying to take your test in December. If you need more time to improve your GMAT score, are you able to schedule your test to a later date?
If you have any questions about my recommendations, I welcome you to contact me directly. I’m here for whatever you need!