My production spreadsheet has thousands of unwanted columns and I am unsure as to how they appeared. I want to delete them. I have tried selecting all of them and deleting them, but nothing happens. I have tried go to > blanks, but it freezes because there are so many columns. Any suggestions?

Also, I tried to copy paste to a new sheet, but the formulas get messed up.

For a mental picture, the spreadsheet is approx 225 rows by 25 columns.

Suggestions would be very appreciated! Thanks!