Gift in nopCommerce

hello every body
I want to set Some gift in my customers cart  :
for each  n Packages of product A i want to set X Packages of Product B as a gift (Product B For free)
sometimes Product A and Product B are same Product and sometimes they are different Products

for example
if you buy a pizza we will send you an extra pizza for free
and other example is :
if you buy a sandwich we will send you a soda for free
and other example :
If you buy 3 burgers we will send you 2 salad for free



i have HasOneProduct plugin but i don't know how should i set it to have this gifts.

You have to use Buy x get y free type plugin. For example https://www.nopcommerce.com/p/3045/buy-x-get-y-free.aspx

thank you for your very much .
i hope to find a free plugin :(
or some help to i write it my self