If you currently have a guest login and it is about to expire, your contact person can extend the guest status and thus the ZIH login. If you do not have a guest status at the moment and would like to keep it, you will find the steps to do so in the FAQ "Guest ZIH Logins".
Select "Guest management" and filter by the desired entries if necessary. You can change the expiration date of an individual guest via the red pencil icon next to the date under "valid until". The new date can be up to 1 year in the future.
You can also extend several guests at the same time by checking the checkboxes under "Selection" and then pressing "Chose new expiry date" under "Bulk actions for all selected guests".
After that you will get a corresponding window, where you can also deregister the guests.