What is the best way to store data statistics in NoSQL?

Question

NoSQL

The situation is this. There is a document describing the data structure with a small nesting. On the site, this structure is displayed in the form of a test. The user clicks everything and you need to collect response statistics.
The question is what is the best way to do it? For each user, create a copy of the structure where the user should be the root. And how to collect statistics from all this? Is there a way to add the same IDs in different documents, or how would it look like?
Maybe there are better options?
I plan to use ArangoDB or RethinkDB.