Floor plan - Conversion into a granny flat experiences?

I would replace the storage room with a closet in each room and divide the rooms as indicated by Kati.

..., and, since it is only supposed to be a WC, one can also create storage space behind a sliding door or something similar in the originally intended bathroom.

However, since we do not know exactly what is supposed to go into the rooms, it is all somehow just guessing and not a reasonably professional workspace planning.