Some people say that it is possible for a blackwhole to evaporate, if so then where does all the matter that fell into it go?
We aren't currently sure, as a lot of what we currently know about black holes are theoretical.
But, judging by what we think we know, if a black hole did evaporate and something had gone into it, it too would get evaporated. There's a lot of theoretical information on this subject and speculations as to what could happen. I would recommend reading this book by Neil deGrasse Tyson, an amazing astrophysicist.
Here is an article/webpage that gives quite a bit of information about Black Holes from Berkeley.