A product add to cart, display multi times, subtotal and total remain single item's price

This is most probably due to a misconfiguration of the view, you might need to turn on aggregation but in any case, support requests are NOT answered from this issue queue:

With the abundance of support available in Drupal Answers, the Drupal focused Stack Exchange site, we are no longer answering support requests in the issue queue.

Support requests opened here will be closed (won't fix), so please search for existing answers or post new questions at:

https://drupal.stackexchange.com (using the drupal-commerce tag)

Also, there is no such thing as a "MAJOR" support request.