CRUD - LARAVEL 5.6

I'm developing a CRUD and in my controller I have the create function:

public function create()
{
    $neighborhood = new Neighborhood();
    $city = new City();
    return view( view: 'admin.cities.create', compact( varname: 'city', _:'neighborhood'));
}

The goal is to create the City and Neighborhood at the same time if you do not have a City-related neighborhood. Below is the View:

@section('content')
    <h3>Nova Cidade</h3>
    <form method="post" action="{{ route('cities.store') }}">
        {{ csrf_field() }}

        <div class="form-group">
            <label for="name">Nome da Cidade</label>
            <input class="form-control" id="name" name="city_name" value="{{ old('name', $city-name) }}">
        </div>

        @if ($neighborhood->id == '')
            <div class="form-group">
                <label for="name">Nome do Bairro</label>
                <input class="form-control" id="name" name="neighborhood_name" value="{{ old('name', $neighborhood->name) }}">
            </div>
        @endif

        <button type="submit" class="btn btn-default">Criar</button>
    </form>
@endsection

My question is how do I save the information in the function store. Here is the function:

public function store(Request $request, City $city, Neighborhood $neighborhood)
{
    $data = $request->all();
    $city->name->$data['city_name'];
    $neighborhood->name->$data['neighborhood'];
    Client::create();
    Neighborhood::create();
    $city->neighborhoods()->create($neighborhood);
}

And below is the error:

  

ErrorException (E_NOTICE)
  Array to string conversion

The error I was able to interpret, so it seems on the line  54 the variable $ data ['city_name'] is an array and must be a string. But how to do this?

I would also like help with the 56 lines that should be to create in the bank and line 57 that creates the neighborhood attached to the city.

I already have a one-to-many relationship in my Model City so I can use the command on line 57. Below is the example.

class City extendes Model
{
    protected $fillable = ['name'];
    public $timestamps = false;

    public function neighborhoods()
    {
        return $this->hasMany( related: Neighborhood::class);
    }
}

I hope I've been able to make myself understood. Thanks in advance for the help.