Insert user register into my own user table instead of wp own user

I figured it out myself I needed $wpdb and a , after the db_name Here is the result.

        $user_id = $wpdb->INSERT( 
            'wp_fisker',
            array (
            'fisker_fornavn' => apply_filters('pre_user_first_name', $fisker_fornavn),
            'fisker_efternavn' => apply_filters('pre_user_last_name', $fisker_efternavn),
            'password' => apply_filters('pre_user_user_pass', $password),
            'telefon' => apply_filters('pre_user_telefon', $telefon),
            'zip' => apply_filters('pre_user_zip', $zip),
            'by_navn' => apply_filters('pre_user_by_navn', $by_navn),
            'email' => apply_filters('pre_user_user_email', $email) 
            )
        );
        if( is_wp_error($user_id) ) {
            $err="Error on user creation.";
        } else {
            do_action('user_register', $user_id);

            $success="You\"re successfully register';
        }