How to sell digital goods through a landing page?

Question

CMS

Purpose: I plan to sell digital goods through the landing.
To do this, the landing should have:
1. The possibility of making a payment with receiving feedback on the completed purchase
2. Client's personal account
3. Administrator 's personal account
Here is the landing:
evick.ru/themforest/brizzz/index.html#prettyPhoto
how can I solve my problem?
are there ready made solutions?
I considered as an option:
1. Transferring a landing page to a ready-made CMS
2. Attach a payment order (a link for payment and a link to the page for downloading a file after payment). But this story is not reliable, there are a lot of holes.
I will be grateful for help.

Answer 1

I found this solution, they also praise it:
ecommtools.com

Answer 2

In the "buy" or "log in to your personal account" form, you direct the user to a certain account, where they either immediately ask for money from him (he has already filled out all the necessary information on the landing page), or ask him for some additional parameters (number of copies, forms return address). After you send the user to the payment, after the payment, catch the user in this account and "give" him the goods.
In both cases, the landing page can live independently in static mode, at least in another data center across the ocean.
You can write an account from scratch, or you can use ready-made cms with the "online store of digital goods" module.
I don't quite understand what the problem is.