when i create a torrent out of some files and add torrent to the public tracker, someone download it.
And now i would like to add some files to the torrent, is that possible and all seeders will also download new files automatically?

UPDATE: this is most probably not possible as the seeders will have old torrent file that do not contain any information about new files. And if they have new updated torrent file/magnet link, it would have different hash and they would have to add it as a new torrent and make sure they download into same location like previous one so not to download old files two times.