Have you tried some of the strategy or reviews guides on verbal? It sounds as though you have no idea what the strategies are for attacking certain CR questions and certain RC questions. There is a PR Verbal review book as well as a Kaplan Verbal review book, both of which contain information about the question types in RC, CR and SC and how to answer them.

As far as MGMAT is concerned, their verbal review is split into individual books. There is one separate book for CR, one for RC, and one for SC. I personally have no experience with the CR and RC book, but I thought the SC book was very thorough especially if you're a non-native English speaker.

If you do not understand how the answer the CR and RC questions, then the OG Verbal review guide will not be much help as it does not contain strategies - it only contains retired GMAT verbal questions. Having said that, the solution explanations are excellent and are mini-lessons in and of themselves so it would still benefit you greatly. However, I still feel you should have another guide that lists out all the question types and how to solve each because the OG explanations will make more sense.