I can help you resolve the issues you requested asap. See this screenshot http://s1.postimg.org/4uruhq1vf/uni_Catow.jpg?noCache=1439857545
All you need to do is use some css to make that part of the background white. Something like this: http://postimg.org/image/9al8jq60r/
The question is what exactly would you like to change? WordPress is organized in such a way that each page is made of many different files controlling different aspects of the site e.g. footer.php controls the footer section, sidebar.php controls the sidebar and so on. What you should do is get the template php file that outputs the static homepage and edit that.
