To resolve issues with German characters ü, ö, and ä, try these steps:
1. Use UTF-8 encoded CSV files for the most reliable results.
2. If you're still having problems, try uploading your data to a public Google Sheet, then download it again as a CSV and attempt the upload once more.
3. Remove commas, colons, and semicolons from your CSV if they're causing field mix-ups.
4. Ensure your CSV uses either commas or semicolons as column separators, but not both.
If these steps don't resolve the issue, you may need further assistance. In that case, request human help by clicking on "Talk to a person" in the chat.