Get Cloud Firestore database collection

I'm trying to get data from my database hierarchy db.collection/doc/collection/

I need to get the data from the collection "product"

I can already filter out the right document, by using this snippet. Still, didn't manage to get any data from the next collection.

db.collection('deliveryservice').where('owner_id', '==', user.uid).collection('product').get().then((snapshot) => {
        snapshot.docs.forEach(doc => {