GP1 490-suggestion to improve score will be appreciated

If you can stick to your study schedule diligently, 2 months is more than enough to improve your score.

First try to get your basics right and then start working on your speed.

For verbal, Manahattan series' sentence correction guide is amazing. For CR and RC, you can try Princeton Review and Kaplan. Also, participate in the discussions on this forum. For RC, just practise as many passages as you can, initially without timing yourself, and later with time limit- average 2 mins per question.

For Maths, you can first go through the Manhattan series books to understand the kind of questions you will encounter in GMAT and to learn tricks for solving the questions faster. Then practise from Kaplan and Princeton Review. Also, participate in the Maths forum on GMATclub, it will surely improve your understanding of concepts.

Once, you feel that you have mastered the basics, try taking few CATs - Princeton and Kaplan books come with CAT CDs. You should do GMATprep tests at the end because GMATprep tests give the most accurate assessment.

Also, doing OG11 is a must but do it only after completing the GMAtprep tests since many of the questions in OG11 are repeated in GMATprep. If you do not have enough time, then just practise the last 50 questions in each section since the questions are arranged by difficulty level.