Black holes are black because everything that enters don't exists anymore.
They are actually extremely red and you see things near them move slowly and the light from then looks very very very red. Like redder than red, like infrared then microwaves then even radio waves. And eventually it is too blurry to really make anything out and too faint (light doesn't bounce off you all the time so fewer bits get back to your friends).
That is why they are sometimes called frozen stars or even red holes.
When you pass the event horizon, the time stops for you, all the future of the universe has passed for you and the universe itself doesn't exists anymore.
This is wrong. You can have two friends with rockets and one heads to a black hole and their friend promises to follow. And of the first friend has enough of a head start they can go through the event horizon and still not know whether their friend had a change of heart and left before crossing the horizon.
What happens is that people far away from the black hole can assign labels to events in ways that correspond to time over where they are. And hey can assign really huge labels to the events before you cross because they will have to wait a huge time to see them. But to you everything feels normal. The event horizon is like a mail man coming by saying this is the last chance to send a letter to your friend if your friend stays on the outside. It doesn't feel like anything.
Relativity. Including all the black holes that evaporated through Hawking Radiation.
That is a separate issue. We ding have a quantum theory of gravity so we don't know for sure what happens. Classically there are events that happen on the outside that you haven't yet seen when you cross. If you take quantum mechanics too then we don't know what happens. But if the black hole evaporated before you got the event horizon then you definitely aren't seeing this'd events in the distant distant future unless you wait a long time.
Larger black holes take more time to evaporate so if you hung out near one then the larger ones would still be around.
In general you don't jump to the distant future just by being near a black hole.
Because of thermodynamics laws, matter must not simply disappear, it must be transformed, back into energy.
This is completely wrong. Things have energy and $E\geq mc^2$ (actually $E^2=(PC)^2+(mc^2)^2.$ So that means that sometimes you can get extra energy from something by slowly it down (so that momentum, $p,$ can become smaller). And sometime you can get even more energy by reducing the mass for instead by combining hydrogen into helium which weighs less or splitting a large nucleus into two parts that weigh less than the original nucleus.
But Because of relativity, its not necessary happens right now in the present, it can and probably happens by the end of the universe,
This is unrelated to mass and energy and thermodynamics.