Horrido and good luck, Corrado!

Taking the "Nordseeküstenradweg" from Wischhafen up to Bremen is not the direct path.
And it could be difficult, cause you're riding upwind til Cuxhaven.

If you're interested in a shorter trail, have a look here

http://www.radweit.de/hbiz/hbiz.html

Starting from Itzehoe (it's on your route, some 50 km north-west of Hamburg)

This route is planned due to the aim "short, no traffic, asphalt if available and no needless altitude" as all the routes on this hp. The author is also a member of this forum.
Nevertheless, the maps need to be studied (and it takes a while, so my experience, to understand the authors instructions) and perhaps, you have to transfer it to your gps.

If help is needed, you're wellcome!