I had my sheet all good, and I think I accidentally press something. What happen is that all my sheet god duplicated and the ones i had was marked as jan(old), feb(old) and so on. But some of the sheet got changed.
How can I undo a mistake I have done?
On the sheet, go to File and See revision history. This will list the changes made on the file and you can easily restore back to the original one by tracking the changes and select which ever is the right version for you.