Hi rheajain and nksbits, it's interesting that you both have similar problems although they're in different topics. The upside is you both have identified where you are weak and you both have plenty of time (5-6 weeks) to correct these weaknesses.
The advice I would give is similar for both of you, so feel free to read the other's paragraph as it may (hopefully) help you in some way as well.
For nksbits, you seem to have identified your problem area as sentence correction. I'm not sure enrolling in a new course will help you, although it couldn't really hurt. The first thing I'd do though is to go over the Sentence Correction questions in the Official Guide. As you can imagine, these are the closest to actual test day questions you're likely to see. Instead of seeing them as disjointed questions, look for overarching themes: Do pronouns vex you? Are you comfortable with timeline questions? Can you properly identify the subject in long passages? Once you've started to notice patterns on these questions, you'll be much more likely to notice similar patterns on GMAT questions you've never seen before. This should help boost your scores. If you're trying to get 750+, though, it might be more than just SC that's holding you back. Is there another area on the test that gives you fits? If so, let me know which and I'll see if I can help.
For rheajain, again you should look for patterns in the questions. If you truly understand the quant concepts, then you should be able to notice a few recurring question types on the exam. If everything seems brand new, then maybe review the theory to ensure you've grasped the concepts. The GMAT tests a finite number of topics, so at some point, you've seen them all. The questions are obviously dressed differently, but that's like me putting on a different shirt. It's the same guy at the core, you just have to recognize me from my camouflage that I'm using today (sort of like Where's Waldo). When you know the concepts forwards and backwards, you may not be able to solve every question, but you'll be pretty sure what the question is getting at when you're trying to work it out.
Hope this helps. Best of luck to you both!
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