Errors starting with swagger project

Hello,
I registered at swagger and created new app (api 3 version)

I modified servers, pointing to my live server :
servers:

# Added by API Auto Mocking Plugin
  - description: SwaggerHub API Auto Mocking
    url: http://vtasks.my-demo-apps.tk
  - url: 'http://vtasks.my-demo-apps.tk'

Is it correct syntax ?

Making first steps I created small part of yml code :

/public_profile:
  get:
    tags:
      - user
    summary: Get public user info by id
    operationId: public_profile
    parameters:
      - name: user_id
        in: path
        description: The user_id that needs to be fetched. Use 1 for testing.
        required: true
        schema:
          type: integer
    responses:
      '200':
        description: successful operation
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/User'
          application/xml:
            schema:
              $ref: '#/components/schemas/User'
      '400':
        description: Invalid username supplied
      '404':
        description: User not found

But when I tried to insert this piece of code, I got erorr:
Cannot set property 'public_profile' of undefined

Why error :

also I tried to test my api for live server, but looks like I got invalid ouput : https://prnt.sc/r2puhp
Not sure, which steps have I to take to run my api on live server ?

Thanks!

Which OS do you use?