You can hide them, assume you need A1:L50,
click the row header number 51 to select that row,
press ctrl + shift and down arrow, do format>row and select hide
now go and select column M, press ctrl + shift and right arrow,
do format>column and select hide
Before you do anything of this you might want to make sure your used range
does not go beyond these dimensions by pressing ctrl + end, if that will go
way beyond expected select like
the rows and columns but press edit>delete first, then save the workbook.
Then hide the cells and finally save the workbook again
You cannot physically delete the rows and columns, and Excel workbook will
always have the number of rows/columns that it's in the specifications. You
can hide them and it will look like
that is all there is