Hey @yijia529 If you use appropriate images for the slider for example demo uses 1400 wide slider img https://themeofwp.com/palette/wp-content/uploads/sites/32/2014/12/02.jpg it’ll be appears in the middle.

Yes green loading bar will be appears at the top of the page this is not an issue. But if you want to hide this bar find the #bar and add display: none; in style.css.

Best Regards
themeofwp.com team