pio2_122
It is not possible to determine the exact geometry of this underground parking lot (nor correctly draw the service roads that are there). However, there is already a marked parking entrance - https://www.openstreetmap.org/node/8785168088 - unfortunately, it is not displayed on the default OSM style. However, it is visible in applications that use OSM data.
I think there is nothing more that can be done in this situation.