ERROR after updating Enfold to 4.8.1

OMG what happend?

I just updated PHP to 8.0.3
then updated WP to 5.7.1 as recommended and all plugins to the newest available version
then updated ENFOLD from 4.7.6.3 to 4.8.1 (manuallly via FTP)

first there was a problem with an old plugin called “SI Captcha for WordPress” wich seems to be outdated and not compatible and the captcha for the backendlogin was broken
there was an ERROR showing:
Warning: Constant FORCE_SSL_ADMIN already defined in /home/.sites/543/site3792348/web/kp/wp-config.php on line 71
so I removed the Plugin manually and also the line 71 in the wp-config.php wich was showing
define(‘FORCE_SSL_ADMIN’, true);
…so far so good, I was able to login to the backend.
everything worked fine for frontend and backend but when I try to edit an existing page it showed me THIS instead of the ALB editing view:

Fatal error: Uncaught ValueError: strrpos(): Argument #3 ($offset) must be contained in argument #1 ($haystack) in /home/.sites/543/site3792348/web/kp/wp-content/plugins/revslider/includes/functions.class.php:387 Stack trace: #0 /home/.sites/543/site3792348/web/kp/wp-content/plugins/revslider/includes/functions.class.php(387): strrpos(”, ‘.’, -1) #1 /home/.sites/543/site3792348/web/kp/wp-content/plugins/revslider/includes/slide.class.php(2345): RevSliderFunctions->check_valid_image(false) #2 /home/.sites/543/site3792348/web/kp/wp-content/plugins/revslider/includes/slider.class.php(2278): RevSliderSlide->get_overview_image_attributes(‘gallery’) #3 /home/.sites/543/site3792348/web/kp/wp-content/plugins/revslider/admin/includes/functions-admin.class.php(212): RevSliderSlider->get_overview_data(Object(RevSliderSlider), Array) #4 /home/.sites/543/site3792348/web/kp/wp-content/plugins/revslider/admin/includes/functions-admin.class.php(128): RevSliderFunctionsAdmin->get_slider_overview() #5 /home/.sites/543/site3792348/web/kp/wp-content/plugins/revslider/admin/includes/shortcode_generator/shortcode_generator.class.php(216): RevSliderFunctionsAdmin->get_short_library() #6 /home/.sites/543/site3792348/web/kp/wp-content/plugins/revslider/admin/includes/shortcode_generator/shortcode_generator.class.php(22): RevSliderShortcodeWizard::add_scripts() #7 /home/.sites/543/site3792348/web/kp/wp-includes/class-wp-hook.php(292): RevSliderShortcodeWizard::enqueue_scripts(‘post.php’) #8 /home/.sites/543/site3792348/web/kp/wp-includes/class-wp-hook.php(316): WP_Hook->apply_filters(NULL, Array) #9 /home/.sites/543/site3792348/web/kp/wp-includes/plugin.php(484): WP_Hook->do_action(Array) #10 /home/.sites/543/site3792348/web/kp/wp-admin/admin-header.php(102): do_action(‘admin_enqueue_s…’, ‘post.php’) #11 /home/.sites/543/site3792348/web/kp/wp-admin/edit-form-blocks.php(450): require_once(‘/home/.sites/54…’) #12 /home/.sites/543/site3792348/web/kp/wp-admin/post.php(187): require(‘/home/.sites/54…’) #13 {main} thrown in /home/.sites/543/site3792348/web/kp/wp-content/plugins/revslider/includes/functions.class.php on line 387

i also got an email containing this:

Fehler-Details
==============
Ein Fehler vom Typ E_ERROR wurde in der Zeile 152 der Datei /home/.sites/543/site3792348/web/kp/wp-content/themes/enfold/functions.php verursacht. Fehlermeldung: Uncaught Error: Failed opening required ‘includes/helper-privacy.php’ (include_path=’.:/usr/local/php5/lib/php’) in /home/.sites/543/site3792348/web/kp/wp-content/themes/enfold/functions.php:152
Stack trace:
#0 /home/.sites/543/site3792348/web/kp/wp-settings.php(528): include()
#1 /home/.sites/543/site3792348/web/kp/wp-config.php(127): require_once(‘/home/.sites/54…’)
#2 /home/.sites/543/site3792348/web/kp/wp-load.php(37): require_once(‘/home/.sites/54…’)
#3 /home/.sites/543/site3792348/web/kp/wp-admin/admin-ajax.php(22): require_once(‘/home/.sites/54…’)
#4 {main}
thrown

PLEASE HELP!!!!
what sahll I do to get it working again?