How can Vue.js simplify a shopping cart or order form?

You model the cart as a reactive array of item objects and let Vue re-render the list whenever that array changes.

Vue.createApp({
  data() {
    return {
      items: [
        { anzahl: 0, name: 'Pizza Margherita', preis: 7.50 },
        { anzahl: 0, name: 'Pizza 4 Stagione', preis: 9.50 },
        { anzahl: 0, name: 'Pizza Fantasia', preis: 11 }
      ]
    }
  },
  methods: {
    /* calculate total */
    sum: function() { }
  }
}).mount('#liste');

Instead of manually updating DOM elements, just modify the items array.