Are you coming recently from Excel? Numbers does things a little differently. Have a look at the templates at File > New in your menu to see good examples of Numbers documents.
In Excel being able to freeze panes or freeze multiple rows can be very important. That's because an Excel worksheet is one large grid of cells, with different areas of the same big grid often used for different purposes.
Numbers takes a more "modular" approach. It is designed to accommodate multiple tables on a sheet. The tables are typically smaller than what you would see in Excel. There is rarely the need to freeze large parts of them.
So I suggest "breaking up" your work into modules to take advantage of the unique Numbers design.
I use both apps and they complement each other well. Numbers is handy for small to medium-sized projects. Excel is better for large datasets and heavy data-wrangling.
SG