find and replace in file xml

i want open file xml and find string then replace. but when replace string Only to find two strings and replace this my code

var realpath = "~/template/xml/xmlback";
var filePath = Path.Combine(HttpContext.Current.Server.MapPath("~/template/xml/xmltest") + ".xml");
var filePath2 = Path.Combine(HttpContext.Current.Server.MapPath("~/template/xml/xmlback/test2") + ".xml");
DirectoryInfo dir = new DirectoryInfo(Path.Combine(HttpContext.Current.Server.MapPath(realpath)));
foreach (FileInfo files in dir.GetFiles())
{
    files.Delete();
}
string strVal = System.IO.File.ReadAllText(Server.MapPath("~/template/xml/xmltest") + ".xml");
strVal = strVal.Replace("Test1", "amir");
strVal = strVal.Replace("Test2", "amir1");
strVal = strVal.Replace("Test3", "amir2");
strVal = strVal.Replace("Test4", "amir3");
strVal = strVal.Replace("Test5", "amir4");
strVal = strVal.Replace("Test6", "amir5");
File.Copy(Path.Combine(filePath), Path.Combine(filePath2));
System.IO.File.WriteAllText(Server.MapPath("~/template/xml/xmlback/test2") + ".xml", strVal);
ProcessRequest(filePath2, Lcourseid.Text);

im try open xml with word and see resultpic