By default, your pages and projects have the reveal on scroll effect enabled. This effect reveals your content while you scroll. If you use tall sections this effect will trigger only when you scroll pass 50% of the section. In this case, the page will be blank until you scroll enough.
To fix this you can use smaller sections. You can create new sections when you drag content on to the page.
You can also disable this effect in the page editor. Click on the "Look & Feel" tab find "Reveal Content on Scroll" and set it to "Disabled." This way his content will appear immediately.