I'm auto-logged-in as my anonymous user and cannot log in as administrator anymore

See example here

You need to add the basic auth in as well

xpack.security.authc.providers:
  basic.basic1:       <!-- This is the normal login
    order: 0  
  anonymous.anonymous1:  <!-- This is the anonymous login
    order: 1
    credentials:
      username: "test"
      password: "askldjfhaslkdjf1654