Show specific price and Basic price in product page (Prestashop 1.7.5.1)

[AZIIZ]

Hello,
I need your help, 
my problem is that I want to show in product page the Basic price and the Specific price of the product (Im using Prestashop 1.7.5.1),
in exemple :
my product price is : 30 €
and I have one group that can buy the product at 20 € (I added it in spécific price)
When the user is not connected, the price shown is 30€, and when connected, the price shown for users from the group is 20 €.
but I want to show for the users of the group the original price of the product (30€) and the specific price (20€).
how can I do this in "product-prices.tpl" ?

Thanks in advance for your help

Edited March 28, 2019 by AZIIZ
more informations (see edit history)