Send verification email when sign up

i’have tried this code but it only access in my application before verifying email.
Also i want to personlise my verification email( action, url, …)
how can i do that
in main.js

firebase.auth().onAuthStateChanged(function (user) {

  if (user) {

        if (user.emailVerified == true) {

        console.log('login success');

            router.push('/users')

          } else {

          router.push('/login')
}
          }

in register.vue
methods: {

    register: function () {

      firebase

        .auth()

        .createUserWithEmailAndPassword(this.email, this.password)

        .then(

          user => {

             var user = firebase.auth().currentUser;

            user.sendEmailVerification();

          },

          err => {

            alert(err.message)

          }

        )

      }

  }

Good morning

Is there anybody who knows the answer?