is it possible to become notified if some file changed on a volumen? With watch_node I can only watch one directory. And with on team I can only watch ~4000 directorys 
If the volume supports queries you can do a live query.
Try something like this in Terminal, or in Tracker if you prefer.
query ‘(last_modified>=%yesterday%)’
You can create a now-timestamp, the usual C-way, and use that instead of %yesterday%.
Check the BeBook on BQuery.