Flow and using JSON to post in MS Teams?

I am new to JSON and do not understand how to use it fully.

So far i have only added a bit of text with JSON posting from Flow to Microsoft Teams.

But all i get to work is

{"text":"some random text"}

As soon as i try to add another textblock or anything else that i google. Flow wont accept it.

Is there limits to what i can use from flow?

Using the app builder in Microsoft Teams.

I can generate this code.

But this wont work atall when i try to use it in Flow

{
  "attachments": [
    {
      "contentType": "application/vnd.microsoft.card.hero",
      "content": {
        "title": "some title",
        "subtitle": "some subtitle",
        "text": "some random text",
        "images": [],
        "buttons": []
      }
    }
  ]
}