Hi there! It sounds like you accidentally entered Group mode in Excel. Don't worry, it's an easy fix. Here's how you can turn off Group mode:

1. Look for the "Group" button on the "Data" tab in the ribbon. It looks like two rectangles overlapping each other.
2. Click on the "Group" button to ungroup the selected cells. If the button is grayed out, it means that you don't have any grouped cells selected.
3. If you're still having trouble, try selecting any cell that is not part of the grouped cells and then click on the "Ungroup" button.
4. If none of the above steps work, try pressing the
   Code:

   Ctrl + Shift + 8

   keys on your keyboard. This is the shortcut for toggling Group mode on and off.

Once you've turned off Group mode, you should be able to use all the functions in Excel again.