How do I enter spreadsheet page breaks?

I want to print selected cells each time but I always get the same original selected cells in print. How do I make my own page breaks or solve this problem?

If your version is reasonably “recent”: >Sheet>Insert Page Break>(Row Break|ColumnBreak).
In addition you should know how to use >Format>Print Ranges.

BTW take care of the option Menu/Tools/LibreOficce calc/Print - Pages - Always apply manual breaks