First of all, note that there is a chance of overwriting data, if the following code is used incorrectly! Be careful!
Now let me explain, that it is important to get the syntax right, because otherwise, rsync will report a write protected file system. You may not access the actual root file system of the storage box.
rsync --progress --delete -e 'ssh -i /home/username/.ssh/test -p23' --recursive /home/username/Downloads/test/ u000000@u000000.your-storagebox.de:test/
Alternatively, you can write ./ before the target directory
rsync --progress --delete -e 'ssh -i /home/username/.ssh/test -p23' --recursive /home/username/Downloads/test/ u000000@u000000.your-storagebox.de:./test/
I recommend to log on via ssh-key, this is the safe way of authenticating. Read Hetzner’s documentation to learn more about the storage box.
