Hi @Red_Stone,
For centering the column headers of your grid view, in our developer docs we have sample code that can be used to accomplish that: CSS Examples
As for centering the grid view’s content, I was able to find a thread where a developer kindly shared their CSS code sample for centering grids and setting the page width: CSS to Change Table Width - #4 by DeanBozzan62116 It may be worth reaching out there in the thread if that sample code doesn’t accomplish what you would like and see if others can help out.
I hope this helps! Thank you for sharing your question 