How to properly update a model on laravel? Method Illuminate\Database\Eloquent\Collection::update does not exist

I made a page for a user to update his company information, all companies default values are null, when a user is created. When a user fills the information, i get this error:

 Method Illuminate\Database\Eloquent\Collection::update does not exist 

I am sure this error is because of my CompanyController@edit

     public function edit(Request $request)
{
    $this->validate($request, [
        'company_name' => 'alpha|max:50',
        'phone' => 'integer|max:50',
        'gst_hst_number' => 'integer|max:50',
        'country' => 'alpha|max:50',
    ]);

    $companies = Company::where('id', Auth::user()->id)->get();

    $companies->update([
        'company_name' => $request->input('company_name'),
        'phone' => $request->input('phone'),
        'gst_hst_number' => $request->input('gst_hst_number'),
        'country' => $request->input('country')
    ]);

    return redirect()->route('company.index')->with('info', 'Company information was updated.');
}

I am stuck quite some time on this issue, would gladly apriciate help and information how to properly update my company models fillable fields.

via Chebli Mohamed