extend incomplete cycleways


within the next week I will go by bike from Viborg in Denmark (“Haervejen”) to Hamburg in Germany (“Ochsenweg”).
Especially south of Schleswig a great part of the “Ochsenweg” is not shown / marked in the map.

I would like to help here and extend the existing marking of this way. However I do not have a glue how to do it.
I already played a bit in the editor somewhere around Pos@: 9.595137 53.856461. There the “Ochsenweg” starts direction south and I just wanted to extend it to north. How can I do it?

An answer in German is also most welcome ;-).