I have a file which is getting downloaded in CSV format, but it has German letters which are not displayed properly in the excel. Some german letters are getting displayed in some different way.
You need to set the proper encoding (unicode utf-8) when importing the file in excel.
For a detailed guide see here:
https://answers.microsoft.com/en-us/msoffice/forum/all/how-to-open-utf-8-csv-file-in-excel-without-mis/1eb15700-d235-441e-8b99-db10fafff3c2
Thankyou @dorilama for the solution.
Happy to help 
Cheers
Mariano