WP crashed at plugin install

Hi,
The installation of the plugin worked fine.
WP Admin page showed the error below when I activated the plug-in.
Since then, no web site, no WP admin interface, just those messages:
Any help would be very much appreciated!
Thanks

Warning: mysql_query(): No such file or directory in /homepages/6/d524799985/htdocs/app524857519/wp-content/plugins/mn-contact-form/mn-contact-form.php on line 79

Warning: mysql_query(): A link to the server could not be established in /homepages/6/d524799985/htdocs/app524857519/wp-content/plugins/mn-contact-form/mn-contact-form.php on line 79

Warning: mysql_query(): No such file or directory in /homepages/6/d524799985/htdocs/app524857519/wp-content/plugins/mn-contact-form/mn-contact-form.php on line 82

Warning: mysql_query(): A link to the server could not be established in /homepages/6/d524799985/htdocs/app524857519/wp-content/plugins/mn-contact-form/mn-contact-form.php on line 82

Warning: mysql_query(): No such file or directory in /homepages/6/d524799985/htdocs/app524857519/wp-content/plugins/mn-contact-form/mn-contact-form.php on line 85

Warning: mysql_query(): A link to the server could not be established in /homepages/6/d524799985/htdocs/app524857519/wp-content/plugins/mn-contact-form/mn-contact-form.php on line 85

Warning: mysql_query(): No such file or directory in /homepages/6/d524799985/htdocs/app524857519/wp-content/plugins/mn-contact-form/mn-contact-form.php on line 88

Warning: mysql_query(): A link to the server could not be established in /homepages/6/d524799985/htdocs/app524857519/wp-content/plugins/mn-contact-form/mn-contact-form.php on line 88

Warning: mysql_query(): No such file or directory in /homepages/6/d524799985/htdocs/app524857519/wp-content/plugins/mn-contact-form/mn-contact-form.php on line 112

Warning: mysql_query(): A link to the server could not be established in /homepages/6/d524799985/htdocs/app524857519/wp-content/plugins/mn-contact-form/mn-contact-form.php on line 112

Warning: Cannot modify header information – headers already sent by (output started at /homepages/6/d524799985/htdocs/app524857519/wp-content/plugins/mn-contact-form/mn-contact-form.php:79) in /homepages/6/d524799985/htdocs/app524857519/wp-login.php on line 418

Warning: Cannot modify header information – headers already sent by (output started at /homepages/6/d524799985/htdocs/app524857519/wp-content/plugins/mn-contact-form/mn-contact-form.php:79) in /homepages/6/d524799985/htdocs/app524857519/wp-login.php on line 431

Warning: Cannot modify header information – headers already sent by (output started at /homepages/6/d524799985/htdocs/app524857519/wp-content/plugins/mn-contact-form/mn-contact-form.php:79) in /homepages/6/d524799985/htdocs/app524857519/wp-includes/pluggable.php on line 913

Warning: Cannot modify header information – headers already sent by (output started at /homepages/6/d524799985/htdocs/app524857519/wp-content/plugins/mn-contact-form/mn-contact-form.php:79) in /homepages/6/d524799985/htdocs/app524857519/wp-includes/pluggable.php on line 914

Warning: Cannot modify header information – headers already sent by (output started at /homepages/6/d524799985/htdocs/app524857519/wp-content/plugins/mn-contact-form/mn-contact-form.php:79) in /homepages/6/d524799985/htdocs/app524857519/wp-includes/pluggable.php on line 915

Warning: Cannot modify header information – headers already sent by (output started at /homepages/6/d524799985/htdocs/app524857519/wp-content/plugins/mn-contact-form/mn-contact-form.php:79) in /homepages/6/d524799985/htdocs/app524857519/wp-includes/pluggable.php on line 1173

https://wordpress.org/plugins/mn-contact-form/