Wilfried, here are my train details

ICE 882, ab München 8:20, ab Kassel-Wilhelmshöhe 11:34, an Hamburg Hbf 13:54
Weiterfahrt mit RE 21020, ab Hamburg Hbf 14:20, an Kiel Hbf 15:36

on the way back:
ICE 927, ab Kiel 12:38, an Hamburg Hbf 13:43
ICE 881, ab Hamburg Hbf 14:05, ab Kassel Wilhelmshöhe 16:25, an München 19:38

I got seat reservations on the 3 ICE trains (but don't yet know which seats as I have not yet got the tickets/reservations)