Adding additional advert after set number of paragraph

There is too much wrong with your ad code for me to attempt guessing what it should be (it has an opening <div> but no closing </div>, it has what appears to be javascript outside of a <script> tag)

...so I skip that part, and simply show how to insert another paragraph instead - this will insert something in the spots you want, and also shows how to use get_post_type() to ensure ads are only shown on posts:

add_filter( 'the_content', 'prefix_insert_post_ads' );function prefix_insert_post_ads( $content ) {    //The last condition here ensures that ads are only added to posts    if ( is_single() && !is_admin() && get_post_type() === 'post' ) {        return prefix_insert_ads( $content );    }    return $content;}function prefix_insert_ads( $content ) {    $closing_p = '</p>';    $paragraphs = explode( $closing_p, $content );    foreach ($paragraphs as $index => $paragraph) {        $paragraphs[$index] .= $closing_p;        if ( in_array($index, array(1, 5, 9)) ) {            //Replace the html here with a valid version of your ad code            $paragraphs[$index] .= '<p style="background:#f00">Ad goes here</p>';        }    }    return implode( '', $paragraphs );}

Check functions in the section of Conditional Tags Index from https://codex.wordpress.org/Function_Reference

if(!is_page()) {    // do your tricks}

There're also some other functions you may need like is_home(), is_front_page() and etc.