Your query in compact Overpass QL:
[out:json][timeout:25];(area["name"="Bern"]["admin_level"="8"]["boundary"="administrative"]->.gemeinde;node["ref:kgs"]["heritage"="2"](area.gemeinde)(46.911695571609,7.3184394836426,46.989503721948,7.4887275695801);area["name"="Bern"]["admin_level"="8"]["boundary"="administrative"]->.gemeinde;way["ref:kgs"]["heritage"="2"](area.gemeinde)(46.911695571609,7.3184394836426,46.989503721948,7.4887275695801);area["name"="Bern"]["admin_level"="8"]["boundary"="administrative"]->.gemeinde;relation["ref:kgs"]["heritage"="2"](area.gemeinde)(46.911695571609,7.3184394836426,46.989503721948,7.4887275695801););out center;