PS: I hope this is not to blunt to ask. It is not meant to be offensive.
PPS: A native speaker could probably ask more politely (sorry about that).
It´s all chill :)
In this case I would like to know what kind of data a (quiz)game created with construct 3 sends (to whome)?
This is up to you. You send what kind of data you want to send. Answers, Student names, IDs, etc. Construct doesn´t send out things on it´s own. And to whom is also up to you, you need a server or use firebase if you don´t have one or don´t want to buy one. Firebase is free unless you have bigger amounts of data.
Final question: the answers would not be encrypted - right?
It depends. If you use SSL the data will be send encrypted otherwise not. Or do you mean some other encryption? There´s also libraries that do encryption and decryption gist.github.com/jo/8619441