Hello,
1) You can’t delete the default header structure. But you can choose to show the other header for the whole site using conditions at the right side https://gyazo.com/bbb67e3ce3635dfea6985c093bbffa53 if the other header is suitable for you.
2) To make the header transparent use the header are bg settings https://gyazo.com/9b68938c9dfd9b84803126684049305a
Provide us with WP Dashboard access if you still have issues with this and tell me which of header layouts you have, suits your needs.
Regards