Please read this doc https://codex.wordpress.org/Function_Reference/comment_form
you may use this code in function.php file of your child theme:
function etheme_move_comment_field_to_bottom( $fields ) {
/**
* Move comment field to bottom.
*/
$comment_field = $fields['comment'];
unset( $fields['comment'] );
$fields['comment'] = $comment_field;
return $fields;
}
add_filter( 'comment_form_fields', 'etheme_move_comment_field_to_bottom' );
and add this css code in Theme Options > Styling > Custom css:
.single-post .comment-respond .form-group[class*=comment]:first-child{padding-left:0px !important;}
.single-post .comment-respond .form-group[class*=comment]:nth-child(2){padding-left:30px !important;}
Regards