You must create two versions of each report: one for German and the other for English. Let the reports have the same name but store them in different directories. Based on the user's language preference, select the report dynamically.
\german\myreport.rpt
\english\myreport.rpt
string GetReportPath(string fileName) {
string folderPath = "";
switch(lang) {
case "german":
folderPath = "\german";
break;
case "english":
default:
folderPath = "\english";
break;
}
return Path.Combine(folderPath, fileName);
}