save and update twitch followings. Javascript

I would like the usernames from user x, which are followed by person x. if I use my function “secondFunction ()” then it adds each new person individually in square brackets. I’m slowly becoming desperate, I want to use the function to add users manually, update followers and remove duplicates. So far it has always overwritten the existing users for me. I was now at the point where they are added and not overwritten. I hope and ask for your help 🙂
I once uploaded the code to jsfiddle so as not to make it too crowded ^^

https://jsfiddle.net/jwqh46xy/

my “con.json” looks like this:

user 5, 6 & 7 would be the ones that were newly added

{
  "applicationid": "123456",
  "token": "123456",
  "access_token": "123456",
  "twitch": {
    "userX": [
      "user1",
      "user2",
      "user3",
      [
        "user5"
      ],
      [
        "user6"
      ],
      [
        "user7"
      ]
    ],
    "user1": [
      "user1",
      "user2",
      "user3",
      [
        "user5"
      ],
      [
        "user6"
      ],
      [
        "user7"
      ]
    ],
    "otherData": {
      "Anything": "value",
      ...
    },
    ...
  }
}

Many thanks in advance