E_ERROR

I am getting an error on my site. I cant book anyting anymore. Also when i look at previos bookings i cant see them and get an error to look at my e-mail. This is what is in my email:Foutdetails
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Een fout van het type E_ERROR werd veroorzaakt op regelnummer 191 van het bestand /home/allure/public_html/wp-content/plugins/salon-booking-system/src/SLN/PostType/Booking.php. Foutmelding: Uncaught Exception: DateTime::__construct(): Failed to parse time string (/2019-09-19 08:00) at position 0 (/): Unexpected character in /home/allure/public_html/wp-content/plugins/salon-booking-system/src/SLN/PostType/Booking.php:191
Stack trace:
#0 /home/allure/public_html/wp-content/plugins/salon-booking-system/src/SLN/PostType/Booking.php(191): DateTime->__construct(‘/2019-09-19 08:…’)
#1 /home/allure/public_html/wp-includes/class-wp-hook.php(286): SLN_PostType_Booking->manage_column(‘booking_date’, 244560)
#2 /home/allure/public_html/wp-includes/class-wp-hook.php(310): WP_Hook->apply_filters(”, Array)
#3 /home/allure/public_html/wp-includes/plugin.php(465): WP_Hook->do_action(Array)
#4 /home/allure/public_html/wp-admin/includes/class-wp-posts-list-table.php(1257): do_action(‘manage_sln_book…’, ‘booking_date’, 244560)
#5 /home/allure/public_html/wp-admin/includes/class-wp-list-table.php(1332): WP_Posts_List_Table->column_default(Object(WP_Post), ‘booking_date’)
#6 /home/allure/public_html/wp-admin/inc

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