hello, i want to take cat exam how can i score for top iims what study material should i study my english is not good.

You can follow below study material for your preparation

1- How to Prepare for Quantitative Aptitude for the CAT Common Admission Test 5th Edition (Paperback) by Arun Sharma

2- The Pearson Guide To Quantitative Aptitude And Data Interpretation For The CAT by Nishit Sinha

3- Quantum CAT: Quantitative Aptitude Common Admission Test for Admission Into IIMs (Paperback) by Sarvesh K Verma

4- NCERT Mathematics books for Class 8, 9 & 10

5- CBSE books for Class 8, 9, 10.

6- How to Prepare for Data Interpretation for the CAT Common Admission Test 1st Edition (Paperback) by Arun Sharma

7-How to Prepare for Logical Reasoning for the CAT Common Admission Test by Arun Sharma

8- The Pearson Guide To Verbal Ability And Logical Reasoning For The CAT 1st Edition (Paperback) by Nishit K. Sinha.

9- How to Prepare for Verbal Ability and Reading  Comprehension for the CAT Common Admission Test 4th Edition (Paperback)  by Meenakshi Upadhyay, Arun Sharma.

10- The Pearson Guide To Verbal Ability And Logical Reasoning For The  CAT 1st Edition (Paperback) by Nishit K. Sinha

To improve English you should read newspapers like The Hindu, The Indian Express, Economics Times and The Statesman.

Good Luck!!

Yes CAT exam this year is expected to be in November/December.
CAT English section consists of questions from grammar, language usage, reading comprehension etc.

Here are some preparation tips for CAT English section:

Develop habit of reading. Read newspapers. You will get a good exposure to learn new words and its pronunciation.
Improve vocabulary.
Do practice last year papers.
Learn the rules of grammar. A lot of questions in CAT exam are based on correction of grammatical errors.

For books:
Refer to Norman Lewis (Word power made easy) this will help you with your basics in English vocab.

You can also refer to arihant  book named English grammar and composition.

Hope these points shall be helpful to you.