How many hours should I spend on studying?

I would spend about 4 hours a day 5 days a week studying. One day taking a practice CAT (after you feel ready). With one off day.

your question is very broad, can you be more specific as to what score do you aim to ....and etc

Your question is too broad to give any specific recommendations BUT you should only spend time studying if it will help. If you stare at your books doing question after question for 6 hours a day you are unlikely to see any real results beyond those that come with increased familiarity with the exam.

I always recommend that students focus their study time - set a goal of what you are going to study for a time period (usually about an hour) and at the end of the hour recap what you have learned that you can take forward to future questions. Also asses whether you accomplished your complete goal or if you have more work to do on the subject. These goals should be specific - I want to study how to work with fractions and understand them, not broad - I will work for an hour on math.

I also recommend that you work on GMAT at least 6 days a week - this isn't something you can study for here and there, it has to become a part of your thinking process.

Good Luck.