When working with CSV files and special characters, such as the German Umlaute, one has to be careful with opening those files in Excel, as often the special characters are not transformed correctly and are saved as such. This results in wrong formatting when uploading the CSV to a Locoia flow or any other system.
As a solution, one should use Sublime Text to handle such files and open them and then Save with Encoding > UTF-8 with BOM. This should preserve the "Umlaute" when you now open the CSV with Excel.
Sublime - Save with Encoding - for encoding issues Excel