Add some more replicas to the deployment and make sure that your deployment spawns 3 pods with the training service instead of one.
https://kubernetes.io/docs/concepts/workloads/controllers/deployment/
Navigate to the app and click the shutdown button for lesson 3. It should shut down one of the nodes and refresh the page after 2 seconds. Since there should now be more replicas, you can click the button a bunch of times and the service will always be up.
Try out a rolling restart with you replicas
kubectl rollout restart ...
https://kubernetes.io/docs/reference/kubectl/cheatsheet/#updating-resources
Watch them again with watch kubectl get pod
Try to convert your Deployment into a StatefulSet (and maybe read what they are about) https://kubernetes.io/docs/concepts/workloads/controllers/statefulset/