Export DataTable to Excel with Open Xml SDK in c#

My program have ability to export some data and DataTable to Excel file (template) In the template I insert the data to some placeholders. It's works very good, but I need to insert a DataTable too... My sample code:

using (Stream OutStream = new MemoryStream())
{
    // read teamplate
    using (var fileStream = File.OpenRead(templatePath))
        fileStream.CopyTo(OutStream);

    // exporting
    Exporting(OutStream);
         
    // to start
    OutStream.Seek(0L, SeekOrigin.Begin);
            
    // out
    using (var resultFile = File.Create(resultPath))
        OutStream.CopyTo(resultFile);

Next method to exporting

private void Exporting(Stream template)
{
    using (var workbook = SpreadsheetDocument.Open(template, true, new OpenSettings                          { AutoSave = true }))
    {
        // Replace shared strings
        SharedStringTablePart sharedStringsPart = workbook.WorkbookPart.SharedStringTablePart;
        IEnumerable<Text> sharedStringTextElements = sharedStringsPart.SharedStringTable.Descendants<Text>();
           
        DoReplace(sharedStringTextElements);
        // Replace inline strings
        IEnumerable<WorksheetPart> worksheetParts = workbook.GetPartsOfType<WorksheetPart>();
          
        foreach (var worksheet in worksheetParts)
        {
            DoReplace(worksheet.Worksheet.Descendants<Text>());
        }

        int z = 40;
        foreach (System.Data.DataRow row in ExcelWorkXLSX.ToOut.Rows)
        {
            for (int i = 0; i < row.ItemArray.Count(); i++)
            { 
                ExcelWorkXLSX.InsertText(workbook, row.ItemArray.ElementAt(i).ToString(), getColumnName(i), Convert.ToUInt32(z)); }
                z++;
            }
        } 
        
    }
}

But this fragment to output DataTable slooooooooooooooooooooooowwwwwww...

How can I export DataTable to Excel fast and truly?