launch new activity from android menu?

Question

I'm new to development, tell me how to open a new activity, I'm failing. mainactivity

  case R.id.about:
        Intent Intent = new Intent(this, AboutActivity.class);
        startActivity(Intent);
        break;

aboutactivity import androidx.appcompat.app.AppCompatActivity;

import android.app.Activity;
import android.os.Bundle;

import com.snappycam.gallery.R;

 public class AboutActivity extends Activity {
/**
 * Called when the activity is first created.
 */
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_about);
}

}

menu

 <item
    android:id="@+id/about"
    android:title="@string/about_app"
    app:showAsAction="never" />

xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout 
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="ui.AboutActivity">
<androidx.appcompat.widget.Toolbar
    android:id="@+id/toolbar"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    app:title="@string/about_app" />
    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello World!"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>