No message in form

I have a User table, which among its variables has a call balance, which is of integer type and is to indicate how much money a user has. I want to make a form which the user writes a number. If the user's balance is zero (or equal to 0), this number will be added as a balance, but if it already had a balance, it will be added to its current amount.

Form:

@extends('layouts.app')
@section('content')

@Logged()
@include('partials.errors')
<form method="POST" action="../saldo">
            {{ csrf_field() }}
            <div class="form-group">
                <label for="saldo" class="col-md-12 control-label"> {{ __("Saldo actual") }}
                </label>
                <input id="saldo" class="form-control" name="saldo" value="{{ old('saldo') }}"/>
            </div>
            <button type="submit" name="addSaldo" class="btn btn-default"> {{ __("Ingresar saldo") }}
            </button>
        </form>
@else
    <h1 class="text-center text-mute" style="color:#FF0000"> {{ __("¡DEJA DE HACER EL INDIO Y INICIA SESIÓN!") }} </h1>
@endLogged
@endsection

web.php:

Route::get('/saldo','UserController@store');

And in method in UserController.php:

public function store(Request $request){

        $normas=[
            'saldo' => 'required',
        ];

        $this->validate($request,$normas);

        if(empty(Auth::user()->saldo))
            Auth::user()->saldo=$request->$saldo;
        else    
            Auth::user()->saldo+=$request->$saldo;
        Auth::user()->save();
        return back()->with('message', ['success', __("Su ingreso se ha efectuado con exito.")]);
    }

But I run the form and I run into this.

And if I put in the first line of store () something like dd ("Ready") I also get the error message. It works if I access directly instead of through the form, so I guess the error is in the form.