Hello!
I have fixed a problem, that was with the game from the beginning. The overlay did not work. However, the reason was that NW.js opens multiple processes and Steam gets confused to which process he should listen to. Now everything is a single process, and every functionality of steam overlay works!
Here is a proof so you do not call me liar:
http://steamcommunity.com/id/yazaa/screenshot/261596055466474358
Thanks for reading!
Yazaa