Sorry, i forgot to put the link to the game:
There's two versions of the game, apparently there's no difference besides one being paid (paid version you start with more gems).
I tried to change the values of the gems, but i can't find the exact adress to do this.
I think it's possible to hack this game, cause suddenly some players appeared from nowhere with a full team of 8 stars heroes, and some players even manage to hack the score of some events.
Anyway, thanks for the help