I do not know who makes the bicycle layer map, but I recently used it in Bavaria. The store where I rented the bikes showed me a better route that was not labeled as a bike route on my iPhone. Who can I contact about this?
Sorry about the very slow response! (We’ve been very busy finishing up a major app update which should be available any day now).
The bicycle layer is defined by data in the OpenStreetMap project in the same manner as our main map layers, and so is created and maintained by a large community of people. Anyone can contribute to help improve these maps through the OSM website, and the tools provided by them. If you have time and interest to get involved you could try to make the improvements yourself (See this Beginners Guide and this specific page about the Cycle Network Tagging), otherwise you could try to contact the part of the community involved in mapping that particular region via their wiki.