Hello send us wp admin url, username and password in a private comment.

You had to select Main Menu and Home Section to Fullscreen Slider in theme options

Yes, you should not add content there. That's just a container you set as a front page. Add content to page-sections .

That's okay. The main page is the one pager does not have any content.

it holds page sections which are added in Main Menu.

if you go to Main Menu you all see what are the page-sections.

Hi, yes, as long is the same project/content, different language versions of the same site are allowed by a single license.