To group and ungroup rows and columns in Google Sheets, follow these steps:
Select the rows or columns that you want to group together. You can do this by clicking and dragging your mouse over the row numbers or column letters.
Once the rows or columns are selected, right-click on them and choose "Group rows" or "Group columns" from the context menu. Alternatively, you can click on "Data" in the menu bar, then select "Group rows" or "Group columns" from the drop-down menu.
The selected rows or columns will be grouped together, and a small triangle will appear at the left side (for rows) or top (for columns) of the group to indicate the grouping.
To ungroup the rows or columns, simply click on the small triangle at the left side (for rows) or top (for columns) of the group and choose "Ungroup rows" or "Ungroup columns" from the options that appear. Alternatively, you can right-click on the group and select "Ungroup rows" or "Ungroup columns" from the context menu.