Hi Anna,
1) Use the following code snippets to delete whole column from the sheet.
[C#]
//Delete the entire row.
sheet.Range["A1"].EntireColumn.Clear();
2) Use the following code snippets to set same font size to whole row.
[c#]
//Set same font size to whole row.
sheet.Range["B1"].EntireRow.CellStyle.Font.Size=20;
sheet.Range["B1"].EntireRow.CellStyle.Font.FontName = "Times New Roman";
Here is the sample for your reference:
EntireRow.zip
Please take a look at the sample above and let me know if you have any other questions.
Thanks,
Melba