The accompanying documents are signed using the “NSUITE-Signature” tool, which you can download when you sign them for the first time. A signature card and a card reader are also required. Supported hardware is listed on the NSuite website:
https://www.nsuite.de/zubehoer
After clicking on Signature, the signature process starts in the NSUITE-Signature program. After successful signing, the document is updated in the Resourcify system. You can close the open NSUITE tab after signing.
Here´s a video explaining how to do this. Sorry it´s just available in german: