Change speed of typewriter / remove background image

- Is it possible to change the speed of the “typewriter” on the home page? Is so, where do I find the correct file(s)/folder(s)?

- How do I add a background image to the full screen header section <div class=”upb_bg_overlay”> (and the equivalent upb_bg_overlay at the bottom of the page)? I want to replace the “dark_road” photo from the template, but can´t locate the right file/folder.