By default, the content you create will appear after the navigation. If you remove your navigation from the page/project you will see the 70px white space on top of your content. Also, if you set your navigation to have a transparent background when you preview your page you will see the white background color.
In order to move your content on top, open your page editor and click "Look & Feel", find "Display Content" option and set it "Straight on Top". Then "Save" and "Publish" your changes.