Hi Niharika,
Your question on how to manage work and GMAT preparation is so relevant during the current times. With everyone working from home, the line between personal life and work-life has blurred.
Let me answer your first question. You don't have to take the exams right away if you are not confident. You can start your GMAT preparation using the OG and take the mock test later. It sii perfectly fine.
And since you are trying to figure out how to manage your work and GMAT preparation, here are a few tips that I would like to share with you:
1. Have a study plan that you can follow. This will help you stay on track.
2. Don't try to study for the GMAT all the time. When you're working, don't think about the GMAT. Focus on your work.
3. Track your productivity on a daily basis. This will keep you motivated.
4. Have an accountability partner. This can be anyone -- your mother, your best friend, your spouse -- who knows your GMAT goal as well as you do.
There are definitely more things that you can do to ensure that you manage your
GMAT preparation along with your work. Please check them out and let me know what you think about them.
Hope these points help you prepare for the GMAT better.