I returned Loren to queen Catherine and the plans to elfking. Then I returned the trumpet to humans. I just dont know how to get the next quest.

Just be patient and take your time. It's perfect time for side quests '-)

Lukier is right, there's a major game event triggered at a certain date, so do some side quests to pass the time, and a messenger will eventually arrive to request your presence at your Harmondale castle.