Excerpt issue problem

I have set up to show the excerpt in my blog,
but when click on the read more link then it jumps to the where the more tag is set up in the post and I do not like it,so I found the below from wordpress to fix this issue by putting some code in the theme function.php. but the problem is that the file for my theme has been encrypted and do not know how to put the codes into it.
anyone can help me with this would be appreciated.
my site is here to see what I mean:
https://myreviewsnbonus.com/

“By default, when you click on the Read More link, the web page loads and then “jumps” to the spot where the <–more–> tag is set in the post. If you do not want that “jump”, you can use this code in your theme’s functions.php :

function remove_more_jump_link($link) {
$offset = strpos($link, ‘#more-‘);
if ($offset) {
$end = strpos($link, ‘”‘,$offset);
}
if ($end) {
$link = substr_replace($link, ”, $offset, $end-$offset);
}
return $link;
}
add_filter(‘the_content_more_link’, ‘remove_more_jump_link’);