> Second step is, of course, if you can even fix them yourself.
It is very likely GP could fix them themself. OpenStreetMap allows for tagging the same map item with different language labels for exactly this reason. OsmAnd is likely simply picking the GP's preferred language, and when that label does not exist, using the language that /is/ available for display.
GP could insert the translations into OpenStreetMap (within the proper language tag) at which point they will be available to everyone using the data, including OsmAnd.
It is very likely GP could fix them themself. OpenStreetMap allows for tagging the same map item with different language labels for exactly this reason. OsmAnd is likely simply picking the GP's preferred language, and when that label does not exist, using the language that /is/ available for display.
GP could insert the translations into OpenStreetMap (within the proper language tag) at which point they will be available to everyone using the data, including OsmAnd.