I have tried to consult Max Maulwurf, but DB have retired him and I can’t find a section on its website about future engineering works. However there appears to be a major bridge replacement due at Neumunster, but no dates are given.
Thanks, doesn't seems to be relevant sadly as trains are running that route just seems Hamburg itself is a mess as even Hannover trains terminate early in harburg, seems to be trackwork around Hbf and that seems crazy to time for peak sylt traffic
Finally did get a booking Hamburg to Copenhagen but dumb how I had to get it done, Schleswig to Copenhagen is compulsory reservation but Hamburg to Schleswig isn't reservable so can't make a direct booking on a train like IC394, so what I've had to end up doing as Schleswig is already filling up so can't wait for Hamburg to Copenhagen to become bookable is book Hamburg to Schleswig as one booking and then another split ticket for the same train Schleswig to Copenhagen with a reservation
Both are refundable so if thru bookings open easy to cancel and rebook and if earlier leg gets cancelled can take RE to Schleswig