Salesforce by default support multi languages, so your user may enter data in their local language. When user run a report, it will show in the correct local language as well.
But, when user click Export Details to export into Excel file, it maybe shown as ???
This may caused by wrong selection of Export File Encoding, to support Non-English characters, make sure to select Unicode (UTF-8) when you export data export into excel.
Screenshot below would be the correct result exported to Excel file.