Does I’mam mahdi really see our a’mal book every week? There is millions of Shia, does he really see each individual person’s A’mal? And also why does he need to see our deeds?

There are some reported traditions that the Imams, including Imam Mahdi (atf), know of our actions and see them. This is likely because if they are to intercede or bear witness on our behalf then they would need to know what we do. Moreover, it is a form of beneficence from them to us, such that they thank Allah when we do good and ask forgiveness (for us) if we mistakenly do wrong.