Most astronauts are a lot more careful than that. Nevertheless, if that were to happen, the gravitational pull of the black hole would either suck them in, never to be seen again, or else rip them apart.
Objects which approach a black hole will get sucked into it.
if you go close enough to a black hole you can get stretched to death the end
It will fall into the black hole. The same happens if something gets too close the Sun, for example - it will fall into the Sun.
When two black holes get close enough together, they might merge, to form a larger black hole.
no one knows
If it gets close enough, it will fall into the black hole. Of course, any object might also pass at a safe distance, with no consequences.
In a black hole, gravity is so strong that nothing, not even light, can escape. This means that whatever goes into a black hole is trapped inside forever, making the saying "what happens in a black hole stays in a black hole" true.
Never or else they would get sucked into it.
For all scientific reasons, no astronaut had went inside a black hole. It would take many earth years to visit the black hole, so reaching a black hole is impossible.
If a star was "too close" to a black hole, that star would be captured by the black hole's gravity and be pulled into it.
if you get to close
That's not exactly what happens. What really happens is that they just absorb each other and become a bigger black hole.