I think that GMAT is built on good command of English. If you have time, go back to the basics of English study, such as sentence structure, vocabulary, and grammar. Understanding is the key. If you feel that you do not understand the question, you need to tackle the basic problems first. Give yourself some time.
What can you do with GMAT of 600? Would that help you in any way? I would say that you take your time.
I can not agree with mindfree more. When I start CR the false ratio is about 40%. I found almost 30% of my false due to the key words, without knowing the word I can not even understand the sentence and my understanding of the whole question would be wrong. So now I start reciting vocabulary together with working on each section of the GMAT.