How to write to a file and read?

Hello! I am making a game for a school contest, and i have a problem, i searched on web but i didn’t found the answer.
My question is, how to make a file, and to write on it, but to write on it in game, i think that i could use the new UI, for user imput. But i don’t know how to make imput to be saved on the file. And after that i need to acces that file and to use what is in it…

My game is like a quiz, where after every question you win something, and i want to make possible that everybody will have the possibility to make their own questions. I used hashtable for questions(is something better than this?), because it seemed more like JSON. Here is an example of one of my questions:

public var question2 = new Hashtable();
	question2.Add(1,"Citi metri sunt in 0,35km?"); // This is the question
	question2.Add(2,"350"); // This is the right answer
	question2.Add(3,"35"); // This is the wrong answer
	question2.Add(4,"3500"); // This is the wrong answer
	question2.Add(5,"35000"); // This is the wrong answer

And i put all questions in an Generic List and then they are choosed randomly from the list…

I think i am clear:( Thanks in advance!

Writing is simple:

string dirPath = Path.Combine(Application.persistentDataPath + "Questions");
if(Directory.Exists(dirPath ) == false){
string filePath = Path.Combine(dirPath, "FileName");
if(File.Exists(filePath) == false){
   File.WriteAllText(filePath, fileAsString);
   File.WriteAllText(filePath, text);