now Question Answer plugin can not design along site theme , beaucase each update , will rebuild it
how to integrate question answer template into site theme



Welcome to our forum.
I am not sure which part you want to redesign from theme file, I guess its single question page, we are using the following hook to overwrite content part from our plugin
question-answer\includes\functions.php line:1635
add_filter( 'the_content', 'qa_single_question_content' );
you can use the following code to remove this hook
remove_filter( 'the_content', 'qa_single_question_content' );
also, another solution by your theme, can create a copy and create single.php to single-question.php
and put your all code to single-question.php file for single question page.
let me know if you any help.