Hi nicki86,
First of all, YOU ARE NOT too stupid for the GMAT, OK?
Believe it or not, you are in the same shoes as many other GMAT test-takers starting their prep from scratch. The good news is that if you can follow a sound and thorough GMAT quant study plan, you can improve your quant skills and one day dominate GMAT quant!
As has been mentioned already, start by taking an
official GMAT practice exam. Your experience taking that test will give you a good idea of what to expect on the GMAT, and the results will serve as a baseline GMAT score. Once you see how far you are from your score goal, you can more easily predict how long you may need to study. Also, I wrote a detailed article about
how long to study for the GMAT, which you may find helpful.
After completing your initial practice test, you will need to devise a solid preparation plan. Since you’re starting from scratch, you should follow a study plan that allows you to learn linearly, such that you can slowly build mastery of one GMAT topic prior to moving on to the next. Within each topic, begin with the foundations and progress toward more advanced concepts. Following such a plan will allow you to methodically build your GMAT quant and verbal skills and ensure that no stone is left unturned. For example, say you’re learning about Number Properties. First, you should develop as much conceptual knowledge about Number Properties as possible. In other words, your goal will be to completely understand properties of factorials, perfect squares, quadratic patterns, LCM, GCF, units digit patterns, divisibility, and remainders, to name a few concepts. After carefully reviewing the conceptual underpinnings of how to answer Number Properties questions, practice by answering 50 or more questions just from Number Properties. When you do dozens of questions of the same type one after the other, you learn just what it takes to get questions of that type correct consistently. If you aren't getting close to 90 percent of questions of a certain type correct, go back and seek to better understand how that type of question works, and then do more questions of that type until you get to around at least 90 percent accuracy in your training. If you get 100 percent of some sets correct, even better. Number Properties is just one example; follow this process for all quant and verbal topics.
When you are working on learning to answer questions of a particular type, start off taking your time, and then seek to speed up as you get more comfortable answering questions of that type. As you do such practice, do a thorough analysis of each question that you don't get right. If you got a remainder question wrong, for instance, ask yourself why. Did you make a careless mistake? Did you not properly apply the remainder formula? Was there a concept you did not understand in the question? By carefully analyzing your mistakes, you will be able to efficiently fix your weaknesses and in turn improve your GMAT skills.
So, work on accuracy and generally finding correct answers, work on specific weaker areas one by one to make them strong areas, and when you take a practice GMAT or the real thing, take all the time per question available to do your absolute best to get right answers consistently. The GMAT is essentially a game of seeing how many right answers you can get in the time allotted. Approach the test with that conception in mind, and focus intently on the question in front of you with one goal in mind: getting a CORRECT answer.
In order to follow the path above, you may consider using a quant self-study course such as
Target Test Prep (as
adkikani mentioned).
You also may find it helpful to read this article about
how to increase your GMAT quant score.
If you have any questions, feel to reach back out.
Good luck!