Hi there Sally!
You might wanna try out the following method:
Under Table Tools, on the Layout tab, in the Table Size group, enter the size that you want in the Height and Width boxes.
To maintain the same ratio between the height and width of the table when you resize it, select the Lock Aspect Ratio check box.
https://support.office.com/en-us/article/move-o...
To completely freeze a table size and it's column size, follow the following instruction:
Select the table, then right click on it.
Go to Table Properties > Under Table tab, click Options... > Uncheck the box of Automatically resize to fit contents > Click OK