Ah ok. I have used a folder "Incoming". all what i dropped there, appears now in the virtual Inbox node. But when i tag the files there, mark all tagged files, right click and choose "send to library" , the files are gone. I couldn't find them in the library.
Currently "auto-organize" is disabled, since i fear that after activating this option, all files in the library where renamed. I didn't want this. I want only to auto-organize new files. It takes a long time to rename all files, since I/O is really slow in my construction. I get mostly not more than 35MB/s, since all files are on the slow Raspberry Pi. This is okay for new files, but not for a whole library with nearby 1TB.