[{title:{de:"Test",en:"test"},infos:[{label:{de:"Test",en:"test"},data:[{label:{de:"Test",en:"test"}},],}],}]

db.collection.aggregate([{$project:{title:"$title.de",infos:{$map:{input:"$infos",in:{$mergeObjects:["$$this",{label:"$$this.label.de"},{data:{$map:{input:"$$this.data",as:"datum",in:{$mergeObjects:["$$datum",{label:"$$datum.label.de"}]}}}}]}}}}}])