Unity LoadContentScene doesn't work as i want

Question

I have a Unity Scene where I put 3 buttons. Every buttons will open another scene on click. The problem that I encoutered is that when I open the scene using the button, the preview scene wouldn't disappear: I see Game Object of first and second scene in the same time but i would see only the second scene Game Object.

There are the steps that i have following:

1. i created the first scene with the buttons;
2. in the button inspector i added the script LoadContentScene and i associated the script to the on Touch function;

Thank you so much.