Does Laposta also keep statistics for each subscriber?

Yes, every action from you and your subscriber is recorded in Laposta. 

On the page Subscribers → View (under Details), you can see the complete history of each subscriber.

Every action you have taken, you can find in this history: all edits you have made in the application for this subscriber, as well as every newsletter you have sent this subscriber.

In this history, you will also find all actions taken by your subscriber, such as every newsletter open, viewing the web version, each click in a newsletter (including the name of the link), the opening of a file and the clicking of a social media button.