PSPO I Certificate

I noticed you haven't yet received a PSM certification.  Although it's certainly not required, a Scrum Master acts as a guide for the PO and should be aware of the same tasks in the Scrum process.  It would be worth looking at the PSM study materials as well as the Scrum Open if you haven't already.  I'd also recommend you skim the Nexus Guide for the sections relevant to Product Ownership, because the PSPO may ask you how the role does (or doesn't) change in a scaled environment.

When you received your email after the exam, it should have contained five categories with percentage ratings for your score in each.  This is to help you identify which areas you've mastered, and which you're weak in.  What areas did you score lower than 85% in?

• Scrum Framework
• Scrum Theory and Principles
• Cross-functional, self-organizing Teams
• Maximizing Value
• Product Backlog Management

Same as Jason, I would recommend to search for some PSM training, a lot of questions are interesting to train. Don't forget to share your willing to take the assessment with other people who already passed it in your company, they may have training QA. Nothing replaces training on QA. A warning though, docs other than Scrum Guide may confuse you by adding some aspects that are not exactly Scrum Framework or Scrum compliant. 

Did you read the book https://www.amazon.com/Professional-Scrum-Product-Owner-Certification-e…;?

I did read the book https://www.amazon.com/Professional-Scrum-Product-Owner-Certification-e… ?  meant for PSPO as it was suggested by some of our community member. Also read CSM -1 book from same author.

May be , I am missing something specially with some tricky question or multi answer.

Two times 84% :( , been demoralizing.  Need to try hard again.