If you want to update the firmware and you are getting an error message that the server ist not available/responding, your phone might have an old update server address inside.
Please log in to the Webinterface of your device and follow the the menu path down to "Settings --> Management --> Firmware Update".
Please enter the following path into the Data server field: profile.gigaset.net/device
Afterwards please klick on the "Set" button. Klicking on the "Update Firmware" button will start the update process if a newer firmware for the device is available.