As said by
@ideaman924, if it says Charging Rapidly, there's problem. Phone thinks it's connected to full-fledged USB Type-C cable which can handle more current than your microUSB cable with converter on the end (3A vs 2A).
AFAIK, it means there's bad/missing resistor in converter and thus it is NOT safe to use. And definitely not safe to charge with all night.
Example: For overnight charging I use Samsung's 5V 1A charger with Anker' a USB A to USB Type-C cable and phone says only Charging. However, when connected to stock Type-C to Type-C charger, it says "Charging Rapidly". That's how it should work.
So, head over to Amazon and buy ONLY Benson Leung certified cable. If you don't know him, Google his name -- he tests USB Type-C cables and made spreadsheet.