Many to many relationship Laravel 7 - many-to-many

Question

OrderController.php
public function create()
{
$user = Auth::user();
//shows only the dishes of the logged user
$dishes = Dish::orderBy("name", "asc")->where('user_id', Auth::id())->get();
return view("admin.orders.create", compact("dishes"));
}
/**
* Store a newly created resource in storage.
*
* #param \Illuminate\Http\Request $request
* #return \Illuminate\Http\Response
*/
public function store(Request $request)
{
$validatedData = $request->validate([
"name" => "required|min:3",
"lastname" => "required|min:3",
"address" => "required",
"email" => "required",
"phone" => "required|min:8",
"total" => "required",
"dishes" => "required",
]);
$order = new Order();
$order->fill($validatedData);
$order->user_id = Auth::id();
$order->save();
//attach dishes to order
foreach ($request->dishes as $dish) {
$order->dishes()->attach($dish, [
"quantity" => $dish["quantity"],
"subtotal" => $dish["subtotal"]
]);
}
return redirect()->route("admin.orders.show", $order->id);
}
/**
* Display the specified resource.
*
* #param \App\Order $order
* #return \Illuminate\Http\Response
*/
public function show($id)
{
return view('admin.orders.show', [
'order' => Order::findOrFail($id)
]);
}
Order model
protected $fillable = [
"name", "lastname", "address", "email", "phone", "total", "user_id"
];
public function dishes()
{
return $this->belongsToMany('App\Dish')
->withPivot('quantity', 'subtotal');
}
I have a problem linking the orders table with the dishes one.
In the pivot table, I also have other columns to link.
What can I do to do this many-to-many relation?
The view I'm doing has the only purpose of trying to save the data into the pivot table.
View create.blade.php
{{-- quantity pivot table --}}
#foreach ($dishes as $dish)
<div class="form-group">
<label for="dish-quantity">Quantità di {{ $dish->name }}</label>
<input id="dish-quantity" type="number" name="dishes[{{ $dish->id }}]"
class="form-control #error('dishes') is-invalid #enderror"
placeholder="Inserisci la quantità" value="{{ old('dishes') }}">
#error('dishes')
<div class="invalid-feedback">{{ $message }}</div>
#enderror
</div>
#endforeach
{{-- subtotal table --}}
#foreach ($dishes as $dish)
<div class="form-group">
<label for="dish-subtotal">Subtotale di {{ $dish->name }}</label>
<input id="dish-subtotal" type="number" name="subtotals[{{ $dish->id }}]"
class="form-control #error('subtotals') is-invalid #enderror"
placeholder="Inserisci il subtotale" value="{{ old('subtotals') }}">
#error('subtotals')
<div class="invalid-feedback">{{ $message }}</div>
#enderror
</div>
#endforeach
{{-- total price --}}
<div class="form-group">
<label for="total_price">Prezzo totale</label>
<input id="total_price" type="text" name="total"
class="form-control #error('total') is-invalid #enderror" placeholder="Inserisci il titolo"
value="{{ old('total') }}" required>
#error('total')
<div class="invalid-feedback">{{ $message }}</div>
#enderror
</div>