Error on updating and saving pages

I bought the parallax-frame-pro theme today. After the problem-free installation and activation of the theme, I get the following error messages when updating and saving pages: ---------------------- Notice: Undefined index: parallax-frame-featured-header-button-target in /homepages/28/d642563536/htdocs/eichholz/wp-content/themes/parallax-frame-pro/inc/metabox.php on line 349 Warning: Cannot modify header information - headers already sent by (output started at /homepages/28/d642563536/htdocs/eichholz/wp-content/themes/parallax-frame-pro/inc/metabox.php:349) in /homepages/28/d642563536/htdocs/eichholz/wp-admin/post.php on line 210 Warning: Cannot modify header information - headers already sent by (output started at /homepages/28/d642563536/htdocs/eichholz/wp-content/themes/parallax-frame-pro/inc/metabox.php:349) in /homepages/28/d642563536/htdocs/eichholz/wp-includes/pluggable.php on line 1223 ---------------------- I urgently need a solution because I'm working on a scheduled project!