Mongodb get all the child documents of given parents in same collection

I am new to MongoDB. I am trying to get all the Users that working under one manager. Following is my collection:

[{
  "_id": {
    "$oid": "6103b24ceb3d6900012eab2b"
  },
  "Name": "Name1",
  "ManagerUserId": ""
}, {
  "_id": {
    "$oid": "611a13c10a69160001a3f45b"
  },
  "Name": "Name1.1",
  "ManagerUserId": "6103b24ceb3d6900012eab2b"
}, {
  "_id": {
    "$oid": "611cb99de9aeb900011a27bf"
  },
  "Name": "Name1.2",
  "ManagerUserId": "6103b24ceb3d6900012eab2b"
}, {
  "_id": {
    "$oid": "611f4d9ba769510001678fa0"
  },
  "Name": "Name1.1.1",
  "ManagerUserId": "611a13c10a69160001a3f45b"
}, {
  "_id": {
    "$oid": "611f4de5a769510001678fa2"
  },
  "Name": "Name1.1.2",
  "ManagerUserId": "611a13c10a69160001a3f45b"
}, {
  "_id": {
    "$oid": "611f5739a769510001678fad"
  },
  "Name": "Name1.2.1",
  "ManagerUserId": "611cb99de9aeb900011a27bf"
}, {
  "_id": {
    "$oid": "611f5779a769510001678faf"
  },
  "Name": "Name1.2.2",
  "ManagerUserId": "611cb99de9aeb900011a27bf"
}, {
  "_id": {
    "$oid": "611f589aa769510001678fb3"
  },
  "Name": "Name1.1.1.1",
  "ManagerUserId": "611f4d9ba769510001678fa0"
}, {
  "_id": {
    "$oid": "611f58f8a769510001678fb5"
  },
  "Name": "Name1.1.1.2",
  "ManagerUserId": "611f4d9ba769510001678fa0"
}, {
  "_id": {
    "$oid": "611f5932a769510001678fb7"
  },
  "Name": "Name1.1.1.3",
  "ManagerUserId": "611f4d9ba769510001678fa0"
}, {
  "_id": {
    "$oid": "611f5976a769510001678fb9"
  },
  "Name": "Name1.1.1.4",
  "ManagerUserId": "611f4d9ba769510001678fa0"
}]

There is N level of hierarchy. I tried following mongo aggregate operation using SO Answer by Neil Lunn

    [{$match: {
  "Name": { $ne: "Name1.1"}
}}, {$addFields: {
"ManagerUserId": { "$toObjectId": "$ManagerUserId" }
}}, {$graphLookup: {
         from: "User",
         startWith: "$ManagerUserId",
         connectFromField: "ManagerUserId",
         connectToField: "_id",
         as: "reportingHierarchy",
         maxDepth:4
}}]

But that resulted in getting all the child in each reportingHierarchy.

I need following output:

[
{
    "_id": {
        "$oid": "611f4d9ba769510001678fa0"
    },
    "Name": "Name1.1.1",
    "ManagerUserId": "611a13c10a69160001a3f45b"
},
{
    "_id": {
        "$oid": "611f4de5a769510001678fa2"
    },
    "Name": "Name1.1.2",
    "ManagerUserId": "611a13c10a69160001a3f45b"
},
{
    "_id": {
        "$oid": "611f589aa769510001678fb3"
    },
    "Name": "Name1.1.1.1",
    "ManagerUserId": "611f4d9ba769510001678fa0"
},
{
    "_id": {
        "$oid": "611f58f8a769510001678fb5"
    },
    "Name": "Name1.1.1.2",
    "ManagerUserId": "611f4d9ba769510001678fa0"
},
{
    "_id": {
        "$oid": "611f5932a769510001678fb7"
    },
    "Name": "Name1.1.1.3",
    "ManagerUserId": "611f4d9ba769510001678fa0"
},
{
    "_id": {
        "$oid": "611f5976a769510001678fb9"
    },
    "Name": "Name1.1.1.4",
    "ManagerUserId": "611f4d9ba769510001678fa0"
}]

In this SO Question it is asked to get ancestor but I am looking for children. Please help me achieving this with mongodb query

Relation _id PK type of ObjcetId ManagerUserId FK(_id) type of string