Q:Est-il possible d'atteindre un trou noir ? Quelle est la distance du trou noir le plus proche de la terre ? Est-ce qu'y a-t-il il un endroit, où le champ de la gravité de la terre est zéro ?

R:

1. There is nothing to prevent one 'reaching', i.e. falling into, a black hole. Indeed, if one approached a black hole too closely and traveling too slowly, there is nothing that could prevent one from being accelerated into the black hole. The first requirement is to find a black hole close enough that one could make the trip from here to there.
2. The nearest multi-million-solar-mass black hole is the one at the centre of our Galaxy. There are many other stellar-mass black holes which are much closer. I would have to dig in the literature to find which one is the closest to us, but I would guess that there is one within a few thousand light years (e.g. Cygnus-X).
3. Anywhere far enough away but ... There is another answer, namely at the centre of Earth. There the gravitational attraction of terrestrial material is equal in all directions, so the net force in any direction is zero.