Ciao ND78

The high and low side of a https://wiki.openstreetmap.org/wiki/Tag:barrier=retaining%20wall is defined by its direction.
Since it seems to me that the lower side is north here, I reversed the direction of the wall in https://www.openstreetmap.org/changeset/147206321

Greetings,
habi 

PS: As stated in the other comment; English or German is fine, whichever you prefer :)