Dear Carsten,
Thank you for sharing file via email.
I tested your file with our latest commercial version (
Spire.XLS Pack(Hotfix) Version:8.8.1), it took only 21 seconds to load your file on my side. If you were using an old version, I would suggest that you upgrade to the latest one to test again. If the speed issue still occurs, please provide your system configuration (E.g. Windows 7, 64-bit) as well as your region setting (E.g. China, Chinese) for further investigation.
Sincerely,
Nina
E-iceblue support team