<?php
$content = apply_filters( 'the_content', get_the_content() );
$contentWithoutHTML = wp_strip_all_tags($content);
$pos = strpos($contentWithoutHTML, " ", 100);
$contentFinal = substr($contentWithoutHTML,0,$pos );
echo $contentFinal . "...";
?>

<?php
$args = array(
    'orderby' => 'ID',
    'order' => 'ASC',
    'posts_per_page' => 7,
    'meta_query' => array(
        array(
            'key' => '_thumbnail_id'
        )
    )
);
$query = new WP_Query($args);
while ($query->have_posts()):
    $query->the_post();
?>
                            <div class="articleboxs boxs">
                                <div class="col-sm-4 noleft">
                                    <div class="aricleleft boxs">
                                      <?php the_post_thumbnail('medium', array(
        'class' => 'img-responsive'
    )) ?>
                                    </div>
                                </div>
                                <div class="col-sm-8 noright">
                                    <div class="aricleright boxs">
                                        <div class="boxs">
                                             <a href="<?php echo get_permalink(); ?>"><h2 class="heading font_Libre"><?php the_title(); ?></h2></a>
                                                <?php
    $content = apply_filters('the_content', get_the_content('', true));
    print_r($content);
    $contentWithoutHTML = wp_strip_all_tags($content);
    $pos = strpos($contentWithoutHTML, " ", 100);
    $contentFinal = substr($contentWithoutHTML, 0, $pos);
?>
                                 <p class="font_Roboto"><?php echo $contentFinal . "..."; ?></p>
                                        </div>
                                    </div>
                                </div>
                            </div>
                          <?php
endwhile;
wp_reset_postdata();
?>

$content = mb_strimwidth(wp_strip_all_tags(get_the_content()), 0, 100, '...');
echo $content;

<?php
$contentWithoutHTML = wp_strip_all_tags($post->post_content);
$pos = strpos($contentWithoutHTML, " ", 100);
$contentFinal = substr($contentWithoutHTML,0,$pos );
?>
<p class="font_Roboto"><?php echo $contentFinal . "..."; ?></p>