Remove default fields and add New

Hi, I am using a theme, which uses cmb2 and WPJobBoard Plugin, There are some default fields under custom post type job listing

https://i.ibb.co/vP605Gn/sah.jpg

I found the code for these input fields here [/wp-content/plugins/wp-job-board/includes/class-job_listing.php] :

$metaboxes[ self::$prefix . 'general' ] = array(
			'id'                        => self::$prefix . 'general',
			'title'                     => __( 'General Options', 'wp-job-board' ),
			'object_types'              => array( 'job_listing' ),
			'context'                   => 'normal',
			'priority'                  => 'high',
			'show_names'                => true,
			'show_in_rest'				=> true,
			'fields'                    => array(

				array(
					'name'              => __( 'Expiry Date', 'wp-job-board' ),
					'id'                => self::$prefix . 'expiry_date',
					'type'              => 'text_date',
					'date_format' 		=> 'Y-m-d',
				),

Removing this code is disabling the custom meta boxes, but as this is core plugin file, I dont what to modify them…

How can I disable these fields using functions.php , and also add new fields … I couldnt find any online resources on this..