I have a class Game that is my main class and a second class Card. Class Card hast its properties and constructor private, only function init is public. Function init checks
I would say don't make the constructor private, don't make the build code under the constructor (place it in a new method, which can be private) and make a method to return the card outside the class.
Then use the card object and call the method to retrieve your card from the Card class, make sure to declare the type Card and make sure that the method returns properly.