Problem with the online store after updating wordpress, php, plugins and themes.

Hello
After updating wordpress, I got these errors:

Warning: Declaration of Envato_Theme_Installer_Skin::feedback($string) should be compatible with WP_Upgrader_Skin::feedback($string, …$args) in /home/krzysztofple/ftp/wp-content/themes/dt-the7/inc/mods/theme-update/envato-wordpress-toolkit-library/class-envato-wordpress-theme-upgrader.php on line 351

Warning: Cannot modify header information – headers already sent by (output started at /home/krzysztofple/ftp/wp-content/themes/dt-the7/inc/mods/theme-update/envato-wordpress-toolkit-library/class-envato-wordpress-theme-upgrader.php:335) in /home/krzysztofple/ftp/wp-includes/functions.php on line 6360

Warning: Cannot modify header information – headers already sent by (output started at /home/krzysztofple/ftp/wp-content/themes/dt-the7/inc/mods/theme-update/envato-wordpress-toolkit-library/class-envato-wordpress-theme-upgrader.php:335) in /home/krzysztofple/ftp/wp-admin/includes/misc.php on line 1310

Warning: Cannot modify header information – headers already sent by (output started at /home/krzysztofple/ftp/wp-content/themes/dt-the7/inc/mods/theme-update/envato-wordpress-toolkit-library/class-envato-wordpress-theme-upgrader.php:335) in /home/krzysztofple/ftp/wp-admin/admin-header.php on line 9

Go Pricing gets a number of errors when trying to enable the plugin:
Warning: Declaration of Envato_Theme_Installer_Skin::feedback($string) should be compatible with WP_Upgrader_Skin::feedback($string, …$args) in /home/krzysztofple/ftp/wp-content/themes/dt-the7/inc/mods/theme-update/envato-wordpress-toolkit-library/class-envato-wordpress-theme-upgrader.php on line 351

Warning: Cannot modify header information – headers already sent by (output started at /home/krzysztofple/ftp/wp-content/themes/dt-the7/inc/mods/theme-update/envato-wordpress-toolkit-library/class-envato-wordpress-theme-upgrader.php:335) in /home/krzysztofple/ftp/wp-includes/functions.php on line 6360

Warning: Cannot modify header information – headers already sent by (output started at /home/krzysztofple/ftp/wp-content/themes/dt-the7/inc/mods/theme-update/envato-wordpress-toolkit-library/class-envato-wordpress-theme-upgrader.php:335) in /home/krzysztofple/ftp/wp-admin/includes/misc.php on line 1310

Warning: Cannot modify header information – headers already sent by (output started at /home/krzysztofple/ftp/wp-content/themes/dt-the7/inc/mods/theme-update/envato-wordpress-toolkit-library/class-envato-wordpress-theme-upgrader.php:335) in /home/krzysztofple/ftp/wp-includes/pluggable.php on line 1296

Warning: Cannot modify header information – headers already sent by (output started at /home/krzysztofple/ftp/wp-content/themes/dt-the7/inc/mods/theme-update/envato-wordpress-toolkit-library/class-envato-wordpress-theme-upgrader.php:335) in /home/krzysztofple/ftp/wp-includes/pluggable.php on line 1299

Warning: Cannot modify header information – headers already sent by (output started at /home/krzysztofple/ftp/wp-content/themes/dt-the7/inc/mods/theme-update/envato-wordpress-toolkit-library/class-envato-wordpress-theme-upgrader.php:335) in /home/krzysztofple/ftp/wp-includes/pluggable.php on line 1296

Warning: Cannot modify header information – headers already sent by (output started at /home/krzysztofple/ftp/wp-content/themes/dt-the7/inc/mods/theme-update/envato-wordpress-toolkit-library/class-envato-wordpress-theme-upgrader.php:335) in /home/krzysztofple/ftp/wp-includes/pluggable.php on line 1299

When trying to enable the plugin, Slider Revolution gets a number of errors:

Warning: Declaration of GW_GoPricing_Plugin_Installer_Skin::feedback($string) should be compatible with WP_Upgrader_Skin::feedback($string, …$args) in /home/krzysztofple/ftp/wp-content/plugins/go_pricing/includes/core/class_plugin_installer_skin.php on line 20

Warning: Declaration of Envato_Theme_Installer_Skin::feedback($string) should be compatible with WP_Upgrader_Skin::feedback($string, …$args) in /home/krzysztofple/ftp/wp-content/themes/dt-the7/inc/mods/theme-update/envato-wordpress-toolkit-library/class-envato-wordpress-theme-upgrader.php on line 351

Warning: Cannot modify header information – headers already sent by (output started at /home/krzysztofple/ftp/wp-content/plugins/go_pricing/includes/core/class_plugin_installer_skin.php:0) in /home/krzysztofple/ftp/wp-includes/functions.php on line 6360

Warning: Cannot modify header information – headers already sent by (output started at /home/krzysztofple/ftp/wp-content/plugins/go_pricing/includes/core/class_plugin_installer_skin.php:0) in /home/krzysztofple/ftp/wp-admin/includes/misc.php on line 1310

Warning: Cannot modify header information – headers already sent by (output started at /home/krzysztofple/ftp/wp-content/plugins/go_pricing/includes/core/class_plugin_installer_skin.php:0) in /home/krzysztofple/ftp/wp-includes/pluggable.php on line 1296

Warning: Cannot modify header information – headers already sent by (output started at /home/krzysztofple/ftp/wp-content/plugins/go_pricing/includes/core/class_plugin_installer_skin.php:0) in /home/krzysztofple/ftp/wp-includes/pluggable.php on line 1299

Fatal error: Uncaught Error: operator not supported for strings in /home/krzysztofple/ftp/wp-content/plugins/revslider/includes/framework/base-admin.class.php:71 Stack trace: #0 /home/krzysztofple/ftp/wp-content/plugins/revslider/admin/revslider-admin.class.php(572): RevSliderBaseAdmin::addMetaBox(‘Revolution Slid…’, ”, Array, NULL) #1 /home/krzysztofple/ftp/wp-content/plugins/revslider/admin/revslider-admin.class.php(73): RevSliderAdmin->addSliderMetaBox() #2 /home/krzysztofple/ftp/wp-content/plugins/revslider/admin/revslider-admin.class.php(44): RevSliderAdmin->init() #3 /home/krzysztofple/ftp/wp-content/plugins/revslider/revslider.php(165): RevSliderAdmin->__construct(‘/home/krzysztof…’) #4 /home/krzysztofple/ftp/wp-admin/includes/plugin.php(670): include_once(‘/home/krzysztof…’) #5 /home/krzysztofple/ftp/wp-admin/plugins.php(58): activate_plugin(‘revslider/revsl…’, ‘https://fototan…’, false) #6 {main} thrown in /home/krzysztofple/ftp/wp-content/plugins/revslider/includes/framework/base-admin.class.php on line 71

I am asking for help in resolving errors because I would like to display the products in a short time. The IT specialist who made this site for me said it was not his problem and that he wanted $ 200 for the repair.

The page I need help with: https://fototaniej.pl

Hi, please contact the author of the theme to get support: