2nd Question gets to the heart of your problem
Both OT and NT START START with the statement that prayer is not about informing God..If you would do some work, you would avoid this
You know when I sit and when I rise;
you perceive my thoughts from afar.
3 You discern my going out and my lying down;
you are familiar with all my ways.
4 Before a word is on my tongue
you, Lord, know it completely.
7 And when you pray, do not keep on babbling like pagans, for they think they will be heard because of their many words. 8 Do not be like them, for your Father knows what you need before you ask him.
The Bible has many passages on why we pray. But your objection was answered 3000 years ago