I got it know, yes was the permission.
But now I have a new issue:
I have set the save game backup to this ftp.
Works fine, all the data are saved to the defined folder.
But in SX Installer they will not be showen.
And I have added the same ftp as new „folder“ in the filemanager, but after I make the game backups I can not access the ftp in the filebrowser. I must readd it and then it works.
This happens everytime I create a backup.