Hello there hinaqui, we are happy to hear you are enjoying our game.
To begin with your first matter, the puzzle helper pretty much is the background image of the mat where the pieces are placed, and the helper part is the image of the background that is placed on the mat so the user has an idea of where the pieces has to fit. Also, the pieces should fit automatically in place when the pieces are released near their correct place, also regarding the sound you mentioned there should be something that indicates if the piece has been placed wrong or when the piece has been placed correctly, also another indication that the piece has been placed correctly would be that you can not pick it up again.
I think some things could have been improved from your feedback, I will keep those in mind for future projects. Thank you for your feedback we really appreciate it.