Wow, very good first attempt! I'm reviewing the layers you made (esp. fuel station and sanitary dump station) and they seem very well done!
I've spotted a few small mistakes, but nothing fundamental.
It would IMHO be even more interesting to have a layer about the canals themselfs, to indicate what types of boats (e.g. small boats, kayaks, ...) are legally allowed to and physically possible to go over a certain waterway; that would be great!
MapComplete is indeed limited to creating new points, but it can modify attributes of existing ways. I'm assuming that most navigable waterways are drawn, but not all necessary attributes are known, where MC could help.
And: tackle it one layer at a time :)