"Leave a comment" after posts to be instead of

Hi there,

Try this:
https://generatepress.com/forums/topic/change-h3-in-comments/#post-821318

Adding PHP: https://docs.generatepress.com/article/adding-php/

Thanks Leo, but we don't have child theme. We use GeneratePress(GP Premium)+Elementor Pro. So which comments.php we must change?

David's code needs to be added using one of these methods:
https://docs.generatepress.com/article/adding-php/

Code Snippets is the easiest method if you aren't using a child theme.