Do i have to do whole level 1 exam again or only fail one in a month time.

You have three attempts for the recertification exam if you don't pass the first time, Kiran.

For the QuickBooks Level 1 ProAdvisor Certification, if you don’t pass on the third attempt, you’ll be locked out of the exam for 10 days. This gives you time to study the modules you didn’t pass and try again. After the 10-day lock-out period passes, you'll have another three attempts to pass the recertification exam.

Check out this link for in-depth information about the renewal process for QuickBooks Certification: FAQs: Renewing your QuickBooks Online Certification: Level 1 and Level 2 (formerly Core & Advanced).

The QuickBooks Community team is fully committed to assisting you with training resources or certification in QuickBooks Online Accountant. Please don’t hesitate to revisit this thread. We are excited to support you at every stage of your journey, Kiran.