Enabling the Responsive layout

You can enable the responsive layout for your Berta with Messy template by turning the responsive layout toggle on, under Design > Page Layout > Responsive design
With this toggle enabled your Berta will keep your design for the desktop and it will make the page auto-responsive for the mobile view.
You can set your page to be fully responsive on desktop and the mobile view by enabling the Grid layout toggle under "Design > Page Layout > Responsive design"

For Default, White and Mashup templates you can do it with the toggle under Design > Page Layout > Responsive design.

That's it, your page is now responsive. :)