Hello, Rafal
Multiple headers, when the custom header is used for the Home page is common practice – https://xstore.helpscoutdocs.com/article/139-cant-see-changes-in-the-header-on-the-home-page
Your main problem with styles was described in the previous reply, we suppose it should be solved from the server side.
If you are not satisfied using our theme you can submit a refund request here – https://themeforest.net/refund_requests/new
Best Regards,
8Themes Team