Hi arnab2312,
Trying to assess your overall readiness to face the GMAT based on how you worked through a sub-set of OG questions is problematic for a number of reasons: the GMAT is adaptive and on a computer, you won't work through all of your SCs "in a row" on Test Day and you'll have to deal with a variety of other factors during the Exam. If you have the knowledge to correctly answer approximately 80% of the SCs in the OG, then that's a solid knowledge-base for SCs and a solid performance - but we can't draw many other deductions from that.
When you posted approximately 3 weeks ago, you had not taken any practice CATs/mocks yet. Have you taken any since then? Before I can offer you any additional advice for your studies, it would help if you could provide a bit more information on how you've been studying and your goals:
1) How many hours do you typically study each week?
2) What study materials have you used besides the OG?
3) On what dates (or approximate dates) did you take EACH of your CATs/mocks and how did you score on EACH (including the Quant and Verbal Scaled Scores for EACH)?
4) Are you planning to take the At-home GMAT or are you planning to take your GMAT at a Test Facility?
5) When are you planning to apply to Business School and what Schools are you planning to apply to? If you are planning to apply sometime soon, then what specific application deadlines are you facing?
GMAT assassins aren't born, they're made,
Rich