how can i add multiple paths to firebase firestore

i tried so many ways but could not find a way to add at least four paths to firestore

my json tree is as follows

ActiveTrades -> Userid -> autogeneratedId -> data fields

Iv tried as follows

var ref = firebase.firestore();
var addOrder = ref.collection("ActiveTrades").doc(userId).add({
 orderId: 1234
});

var ref = firebase.firestore();
var addOrder = ref.doc("ActiveTrades/"+userid).add({
 orderId: 1234
});

Please help