[{"_id":"123456","enabled":true,"entity":{"name":[{"locale":"en","value":"Lithuania"},{"locale":"de","value":"Litauen"}]}}]

db.collection.aggregate([{$project:{country:{$reduce:{input:"$entity.name",initialValue:"",in:{$cond:[{$eq:["$$this.locale","en"]},"$$this.value","$$value"]}}}}}])