problem module preorder and import and totals in cart

[carlitus]

Hello,
 
To carry out the sale with preorder in order to charge a percentage in the sale and then the rest, we have installed the module https://addons.prestashop.com/es/inscripcion-proceso-del-pedido/17707-pre-order.html

The problem is that once applied the percentage of discount in the tab of the product to add it to the cart, this always takes the normal price of the product and not the partial fraction calculated, and in all places that the cart shows badly The amount of the product and the total of purchase.

I am not an expert but I intuit that I should tweak the cart module so that in any place it apply the discount on the price ( the module does not do it) but I do not know where to start or where to overwrite the amounts and totals.

Use prestashop 1.7.1.2

I need to fix it.

Any suggestions? thank you very much.