Thanks. You won't be able to delete that bottom section because it is the Body of the website. Your website is composed of three sections: Header, Body, and Footer. To fix this, you will need to move all of the content from the header down to the body. You can do this by drag/dropping the elements one by one into the body to make sure everything stays lined up properly. I tried to make a copy of the page to show you an example, but the third party apps did not copy to the new page. As a hint, if you hover over the elements you may see multiple elements grouped together. You can move all of these elements at once as long as the blue outline covers the multiple elements.
To move elements, click on the column (or hover over the element) and click on the lego/brick looking icon at the top. You can click/grab this to move the element down into the body.
The copy page is still available if you want to practice moving elements before working on the original page. Click on pages, then "copy - Muses"
