Getting error while using OpenXML for Excel Export

i'am trying to export data to Excel. For that purpose i use OpenXML.

The Structure of the Excel should look like this:

My current Code:

public void CreateExcelDoc(string fileName)
{
using (SpreadsheetDocument document = SpreadsheetDocument.Create(fileName, SpreadsheetDocumentType.Workbook))
{
WorkbookPart workbookPart = document.AddWorkbookPart();
workbookPart.Workbook = new Workbook();
WorksheetPart worksheetPart = workbookPart.AddNewPart();
worksheetPart.Worksheet = new Worksheet();
Sheets sheets = workbookPart.Workbook.AppendChild(new Sheets());
Sheet sheet = new Sheet() { Id = workbookPart.GetIdOfPart(worksheetPart), SheetId = 1, Name = "Test Sheet" };
sheets.Append(sheet);
workbookPart.Workbook.Save();
SheetData sheetData = worksheetPart.Worksheet.AppendChild(new SheetData());
// Constructing header
Row row = new Row();
row.Append(
ConstructCell("Vendor Name", CellValues.String),
ConstructCell("Vendor Mail", CellValues.String),
ConstructCell("Vendor Adress", CellValues.String),
ConstructCell("Vendor Phone", CellValues.String));
// Insert the header row to the Sheet Data
sheetData.AppendChild(row);
ServicesExportDataProvider dp = new ServicesExportDataProvider();
var vendors = dp.GetVendors();
// Inserting each vendor
foreach (var vendor in vendors)
{
row = new Row();
row.Append(
ConstructCell(vendor.VendorName, CellValues.String),
ConstructCell(vendor.VendorMail, CellValues.String),
ConstructCell(vendor.VendorAdress, CellValues.String),
ConstructCell(vendor.VendorPhone, CellValues.String));
sheetData.AppendChild(row);
}
InsertEmptyRow();
Column column = new Column();
Cell cell = ConstructCell("Info", CellValues.String);
column.Append(cell); // **<--- Creates the Exception**
sheetData.AppendChild(column);
worksheetPart.Worksheet.Save();
}
}

I can export the "Vendors" - Lines. But if i try then to Create columns to Export the "Item Information" vertically, i get the following error:

Non-composite elements do not have child elements

Column column = new Column();
Cell cell = ConstructCell("Info", CellValues.String);
column.Append(cell); // **<--- This line throws the error

I can't figure out the problem. Do you have any ideas? How can I Export data in the structure of "Item Information"?