Welcome to the club that no one wants to be in! You will find a lot of information on this forum by members with far more experience then me. Keep in mind that what you read on these online forums are mostly from people that are having bad side effects. Don't let that scare you as there are many more people that have no side effects and no need to post on these forums.

I think you meant PIRADS 5 from the MRI. This means the lesion is highly likely cancer. The Biopsy is the correct next step to grade the cancer. Then a PSMA PET/CT scan would be best to have and perhaps a decipher test. Sometimes a 2nd opinion on biopsy slides helps but not always necessary if you are being seen by a top cancer center. I would not jump to surgery. Many who have surgery end up needing radiation anyway and also have side effects. Take your time to look at all options and get 2nd & even 3rd opinions. There are so many options to choose from. PC is a slow moving cancer. Do your research.
Best of luck.