How to set up the goal of payment for an order on an html site in Analytics?

Question

PHP

The site is developed on HTML, fastened payment through payment systems paymaster and paypal. Upon successful payment, the user is returned to a certain page (/indexsuc.php).
It is important for us to understand the chain of movement of the client:
1. where and on what request the user came to inpresso.ru
2. what sections of the site he viewed and what tariff he chose
3. whether he paid the tariff or not
4. whether the client made a call on the site
Our site : goo.gl/RQDwEI
Ultimately, we will understand how much the customer who made the purchase cost us.
Share your experience and recommendations on how best to organize the scheme.

Answer 1

1) you won’t be very lucky with the request
2) here, too, it can climb so that where it’s not clear where, but in general, something can be done with tags
3) the percentage of unaccounted for is also
set to logged ID through user GA parameters

Answer 2

Set the purpose of payment for the order - according to the URL of your thank you page. But where did you come from and from what request - this is a very difficult question, custom parameters, as mentioned above, will help. A call is a completely different story - call tracking to help.
Whether the payment was made - can be implemented using e-commerce, passing this information from your server to the GA through your conversion page.