For the statistics tracking to work properly, you must launch the game directly from GOG GALAXY 2.0.
Also make sure you have an uninterrupted connection to the Internet and that GOG GALAXY 2.0 runs in the background while you play the game. Tracking statistics requires that you be connected to the Internet when you exit the game, as only one update of statistics is performed at that time.
You must ensure that your security software (anti-virus, anti-spyware, firewall, etc.) does not interfere with GOG GALAXY 2.0. To do this, make sure that GOG GALAXY 2.0 is added to the list of reliable / trusted applications in the software (the procedure varies depending on the security software).