Try the below code. I think its working.

<?php
	$args = array(  
		'post_type' => 'post',
		's' => $searchinput,
		'posts_per_page'         => '3',
		'paged'                  => $paged
	);
	query_posts( $args );
	$posts= get_posts( $args );
	if ($posts) {
	    foreach ( $posts as $post ) {
	        setup_postdata($post);
	        ?>
	        <div class="chinaseredivs">
		        <a>	 
		        	<?php 
		        		if(get_the_post_thumbnail( $post->ID, 'thumbnail' )){
		        			echo get_the_post_thumbnail( $post->ID, 'thumbnail' );
		        		} 
		        		else{
		        			echo '<img src="https://via.placeholder.com/350x150" />';
		        		}
		        	?>
		       		<h3 class="chinasearchrepost"><?php the_title(); ?></h3>
		        	<?php
		        		$content=get_the_content();
		        	?>
		        	<p class="chinasearchrepost"><?php echo wp_trim_words($content, 40,'...'); ?></p>
	        	</a>
	        </div>
			<?php
	    }
	    the_posts_pagination( array(
	    	'mid_size'=>3,
		 	'prev_text' => _( 'Back'),
		  	'next_text' => _( 'Next'),
		) );
	}
?>

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