Your robotic lawnmower can be updated via the GARDENA smart system. However, this only affects the ""smart functions"" of your device and not the base firmware update.
To update the base software of your robotic lawnmower to the latest version, please click on the following link and follow the steps provided:
https://www.gardena.com/int/c/support/planning-advice/robotic-lawnmowers/maintenance/software-update