fatal error after latest update

Hello!
After updating my theme I got the following error message. I cannot access my page as admin any longer, neither can anyone view my website anymore. (http://prowaldeck.de/)
This happened yesterday at about 12 pm. Could the theme with the previous version I used until yesterday morning be installed again?
Fatal error: Cannot redeclare palm_beach_magazine_posts_excerpt_length() (previously declared in /homepages/4/d583359868/htdocs/prowaldeck/wp-content/themes/prowaldeck/inc/magazine.php:43) in /homepages/4/d583359868/htdocs/prowaldeck/wp-content/themes/palm-beach/inc/magazine.php on line 80