admin login page error

Hi there, I am not an experienced user of WP. I lately updated a few plugins in my friends website and now when I want to login into the admin platform, the site looks like doesnt exist. It says there are 2 errors:

Notice: Undefined index: exclude_from_search in /var/www/vhosts/1/125984/webspace/siteapps/WordPress-11170/htdocs/wp-content/plugins/lite-event-calendar/functions.php on line 455 Notice: Undefined index: events_slug in /var/www/vhosts/1/125984/webspace/siteapps/WordPress-11170/htdocs/wp-content/plugins/lite-event-calendar/functions.php on line 459

It unfortunately does not work at any other computer.

Could you help me someone plese?

Thanks, Petra