Laravel: Product Update/ Method update does not exist

Trying to update my Auth:user() Product with update method, but always results in Error. User has many products() / Product belongsTo user().

$this->validate($request, [

            'title'=> 'max:140',
            'brand'=> 'max:140',
            'sku'=> 'max:140',
            'description'=> 'max:140',
            'price'=> 'max:140',
            'availability'=> 'max:140',

        ]);

        $product = auth()->user()->products()->findOrFail($id);

        $product->update([

            'title' => $request->input('title'),
            'brand' => $request->input('brand'),
            'sku' => $request->input('sku'),
            'description' => $request->input('description'),
            'price' => $request->input('price'),
            'availability' => $request->input('availability'),

        ]);

Am I missing something within my Controller? Btw.

Auth::user()->products()->update([
            'title' => $request->input('title'),
            'brand' => $request->input('brand'),
            'sku' => $request->input('sku'),
            'description' => $request->input('description'),
            'price' => $request->input('price'),
            'availability' => $request->input('availability'),
]);

updated every User related product to the same values.

So the problem is within the Product specification.

Any suggestions? Thank you

via Chebli Mohamed