Dear,
I have 4+ year development experience in android.
I have developed many apps and integrated payment gateway as well.
As per my understanding you need to add a new tab where in calculation must be done of score based on user sharing the content. you need to put offer and once he accomplish it, he must redeam from paypal.
I confident to complete it in 1 day.
Lets chat, discuss it in detail and close the project.
Thanks.