Updating website to a Progressive Web App

I want to upgrade my website to a PWA(Progressive Web App). For this I already implemented some things in my code:

index.html

<script>
      if('serviceWorker' in navigator) {
        navigator.serviceWorker.register('/sw.js')
          .then(function() {
                console.log('Service Worker Registered');
          });
      }
    </script>  

sw.js

var cacheName = 'kaffboard_alpha';
var filesToCache = [
  '/',
  '/index.html',
  '/index.js',
  '/style.css'
];

self.addEventListener('install', function(e) {
  console.log('[ServiceWorker] Install');
  e.waitUntil(
    caches.open(cacheName).then(function(cache) {
      console.log('[ServiceWorker] Caching app shell');
      return cache.addAll(filesToCache);
    })
  );
});

self.addEventListener('activate',  event => {
  event.waitUntil(self.clients.claim());
});

self.addEventListener('fetch', event => {
  event.respondWith(
    caches.match(event.request, {ignoreSearch:true}).then(response => {
      return response || fetch(event.request);
    })
  );
});

Unfortunately, I got these two errors:

I think only the second error is caused by the SW. I use Firebase Hosting. After I deploy the site it even does not work offline.