Talk:City of Basel Suburb Import
Did you made the conversion manually?
I made a python tool years ago to convert boundaries to OSM from shapefiles https://wiki.openstreetmap.org/wiki/User:Capiscuas
Mine is at https://github.com/capiscuas/libreGTFS/tree/master/other but it is customized a bit depending on the labels of the SHP file.
Please be sure to tag each suburb with the ID of the equivalent Wikidata item. They all seem to be available here: