Your property manager for the building remains as-is. In almost all cases, matters concerning the whole building (common property, "Gemeinschaftseigentum") are managed by a property manager, "WEG-Verwaltung" whose duties are prescribed by regulation.
Home manages your apartment. Home takes care of all topics that relate to your apartment specifically (separate property, "Sondereigentum"). Some property managers offer additional services beyond the managing the building. You can always use Home. However, it might make sense to double check if you need all the services of your current property manager.