change the search.php

Hey all,

the following problem:

I need a networkwide search engine, tried some plugins, don’t work the way they should, now i found a nice article: search-across-wp-multisite

And I want to change the search.php as mentioned, but my problem was step 3, the replacements, because most of them are not given -.-‘

Do I have to change the whole search.php to make it work?

Here is my search.php, working with the AVADA Theme

<?php

// Do not allow directly accessing this file.
if ( ! defined( 'ABSPATH' ) ) {
	exit( 'Direct script access denied.' );
}
?>
<?php get_header(); ?>
<div id="content" <?php Avada()->layout->add_class( 'content_class' ); ?> <?php Avada()->layout->add_style( 'content_style' ); ?>>
	<?php if ( have_posts() && 0 != strlen( trim( get_search_query() ) ) ) : ?>

		<?php if ( 'bottom' == Avada()->settings->get( 'search_new_search_position' ) ) : ?>
			<?php get_template_part( 'templates/blog', 'layout' ); ?>
			<div class="fusion-clearfix"></div>
		<?php endif; ?>

		<?php if ( 'hidden' != Avada()->settings->get( 'search_new_search_position' ) ) : ?>
			<div class="search-page-search-form search-page-search-form-<?php echo Avada()->settings->get( 'search_new_search_position' ); ?>">
				<?php
				/**
				 * Render the post title
				 */
				echo avada_render_post_title( 0, false, esc_html__( 'Need a new search?', 'Avada' ) );
				?>
				<p><?php esc_html_e( 'If you didn\'t find what you were looking for, try a new search!', 'Avada' ); ?></p>
				<form class="searchform seach-form" role="search" method="get" action="<?php echo home_url( '/' ); ?>">
					<div class="search-table">
						<div class="search-field">
							<label class="screen-reader-text" for="searchform"><?php _e( 'Search for:', 'Avada' ); ?></label>
							<input id="searchform" type="text" value="" name="s" class="s" placeholder="<?php esc_html_e( 'Search ...', 'Avada' ); ?>"/>
						</div>
						<div class="search-button">
							<input type="submit" class="searchsubmit" value="" />
						</div>
					</div>
				</form>
			</div>
		<?php endif; ?>

		<?php if ( 'top' == Avada()->settings->get( 'search_new_search_position' ) || 'hidden' == Avada()->settings->get( 'search_new_search_position' ) ) : ?>
			<?php get_template_part( 'templates/blog', 'layout' ); ?>
		<?php endif; ?>

	<?php else : ?>

		<div class="post-content">

			<?php echo Avada()->template->title_template( esc_html__( 'Couldn\'t find what you\'re looking for!', 'Avada' ) ); ?>
			<div class="error-page">
				<div class="fusion-columns fusion-columns-3">
					<div class="fusion-column col-lg-4 col-md-4 col-sm-4">
						<h1 class="oops"><?php esc_html_e( 'Oops!', 'Avada' ); ?></h1>
					</div>
					<div class="fusion-column col-lg-4 col-md-4 col-sm-4 useful-links">
						<h3><?php esc_html_e( 'Helpful Links:', 'Avada' ); ?></h3>
						<?php $circle_class = ( Avada()->settings->get( 'checklist_circle' ) ) ? 'circle-yes' : 'circle-no'; ?>
						<?php wp_nav_menu( array(
							'theme_location' => '404_pages',
							'depth'          => 1,
							'container'      => false,
							'menu_class'     => 'error-menu list-icon list-icon-arrow ' . $circle_class,
							'echo'           => 1,
						) ); ?>
					</div>
					<div class="fusion-column col-lg-4 col-md-4 col-sm-4">
						<h3><?php esc_html_e( 'Try again', 'Avada' ); ?></h3>
						<p><?php esc_html_e( 'If you want to rephrase your query, here is your chance:', 'Avada' ); ?></p>
						<?php echo get_search_form( false ); ?>
					</div>
				</div>
			</div>
		</div>
	<?php endif; ?>
</div>
<?php do_action( 'avada_after_content' ); ?>
<?php get_footer();

/* Omit closing PHP tag to avoid "Headers already sent" issues. */

Hope someone can help