ashkanator wrote:
is it adviceable to do a 4 weeks self prep for the gmat or this would prove to be unwise?
It's possible, but certainly not easy. It all depends on how competitive you want to be and how well you typically do on these kinds of exams.
Only you can tell how well you normally do on standardized exams that test reasoning, math, and writing skills. Try to take a look at your previous standardized exam scores as a benchmark for how you might fare on the GMAT exam.
If you scored above 90th percentile on the SAT in both/all sections, you might be OK with self-studying to get above the 80th percentile mark on the GMAT--as long as you put in the effort. If you haven't done well in past standardized exams--well, you probably shouldn't expect a super stellar score on the GMAT either.
Obviously, you need to consider lots of different factors. For example, the SAT is taken by almost every high school student in the United States. The GMAT is taken only by those who are seriously considering business school. So the applicant pool with the GMAT exam is certainly more competitive---and global.
If you find someone to teach you how to think differently and more effectively on the GMAT---you could see significant improvement. For some that means browsing these forums. For others, it means taking a course or finding a private tutor. Only you know the learning style that fits you best.