Question: How to rearrange matrix and making them smaller

Hi, I have a 9x9 matrix. I am trying to add the last column to the first column, and vanish the last column, leaving me with a 9x8 matrix. Then add the last row to the first row, and vanish the last row, leaving me with a 8x8 matrix. I would like to repeat the process till i'm left with a 6x6 matrix. May I  know how could i do it please.

I am currently moving it one by one, but is not efficeint when i'm doing a few sets of 9x9 matrix. Could I know if it is possible to do it all in a loop please? Thank you.

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