Fatal error: Uncaught Error. How to solve it?

I have a problem with my site, but I don’t know what happened and how to fix it! 🙁

Can somebody help me? Thanks in advance.

This is the error:

Fatal error: Uncaught Error: Call to a member function get() on boolean in /membri/studiaremedicina/wp-content/plugins/themegrill-demo-importer/includes/admin/class-pro-theme-notice.php:86 Stack trace: #0 /membri/studiaremedicina/wp-includes/class-wp-hook.php(288): TG_Pro_Theme_Notice->pro_theme_notice(”) #1 /membri/studiaremedicina/wp-includes/class-wp-hook.php(312): WP_Hook->apply_filters(NULL, Array) #2 /membri/studiaremedicina/wp-includes/plugin.php(478): WP_Hook->do_action(Array) #3 /membri/studiaremedicina/wp-settings.php(510): do_action(‘after_setup_the…’) #4 /membri/studiaremedicina/wp-config.php(26): require_once(‘/membri/studiar…’) #5 /membri/studiaremedicina/wp-load.php(39): require_once(‘/membri/studiar…’) #6 /membri/studiaremedicina/wp-blog-header.php(13): require_once(‘/membri/studiar…’) #7 /membri/studiaremedicina/index.php(17): require(‘/membri/studiar…’) #8 {main} thrown in /membri/studiaremedicina/wp-content/plugins/themegrill-demo-importer/includes/admin/class-pro-theme-notice.php on line 86
Si è verificato un errore critico sul tuo sito web.

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