Hi Bledi,
the 10-mins break is the only chance you have to take a break during the PMP exam in the online proctored mode (I'm not sure about how it works at a testing center). When prompted, I had the option to skip the break, but the first part of the exam remains submitted and not accessible anymore. I took the break, as it was much needed for me. Also, it is extra time with respect to the 4-h exam; I highly recommend taking it!
Nevertheless, you can review the flagged questions (or even all the questions, as you wish) before submitting the first part of the exam—same holds for the last part. Once you confirm that you are ready to submit it (the system will ask you twice, so don't worry: you won't submit it by mistake

), you will be asked whether you want to start the break or move to the second part of the exam.
Gabriella