Hi Andreas,
I’m sorry to hear about the trouble you’re experiencing. Can you confirm if this file is from Clay and whether it includes the “created at” or “updated at” column?
If not already done, please try uploading the file to Google Sheets, re-exporting it as a CSV, and then uploading it to Clay.
If that doesn’t resolve the issue, could you share the Google Sheets Public URL with us? I’ll be happy to take a closer look. Let me know if you need further assistance!