On this point what was the thought process of canonizing nach. Also what does it mean that they canonized it neviim I understand wherever it says "So says God", that’s God speaking so what about ketuvim and the history/story parts of neviim? Also why is the "So said God" on a lower level than the Torah if they are both God speaking? And when did they do it did it happen all at once or when the books were written the sanhedrin gave there stamp of approval? Also when the sanhedrin returns by moshiach can they make more sefarim part of tanach Thanks

What was written in prophecy (even the historical parts) and needed for future generations was canonized into Nevi'im. The Torah is not just prophecy but Moshe's prophecy which was on a qualitatively higher level (the famous Rambam details the 3 major differences). On the other hand, Ketuvim is not prophecy but Rua'ch HaKodesh, a 3rd and clearly lower level. The books entered at different times, where the last books to be canonized are Chronicles, which occurred, was written and entered around the year 500 BCE. [Nevertheless, there were different opinions around the year 100 CE whether Ecclesiastes and the Song of Songs (which were written by Solomon about the year 1000 BCE) should stay in, for the masses may easily misunderstand them. It was decided to leave them in.] No, there will be no additional books added in the future.