The Telegraph explored some of the science of Interstellar:
Miller’s planet is as close to the huge black hole Gargantua as it can
be without getting sucked in.
The crew of Interstellar’s Endurance spaceship faced a headache when
trying to get to Miller’s planet because it is trapped within the
control of the huge black hole Gargantua.
To avoid being sucked into the black hole, the spaceship had to be
travelling at high speed to escape the huge gravitational and
In Interstellar, Cooper gets round his speed dilemma by slingshotting
around a the black hole.
However the speed needed to escape something as massive as Gargantua
is huge. The Endurance would need to be travelling at close to the
speed of light to escape the huge pull of the black hole, and then
quickly slow down so it could land on the planet. The sudden change in
momentum would almost certainly tear the ship apart.
There's a similar question on Science Fiction & Fantasy Stack Exchange. It got closed down for being off-topic but it has an answer about black holes in general.
There is another question on the SF&F SE where the answer contains some relevant information. It cites information from The Science of Interstellar by physicist Kip Thorne (who was a consultant on the movie, and co-wrote the original script treatment):
As for how they manage to navigate from one orbit to another, Thorne
discusses this in chapter 7. Basically his answer is that although
their rockets alone wouldn't be sufficient, they use gravitational
slingshots past other massive objects in orbit around Gargantua,
including smaller black holes and neutron stars.
There's a long excerpt that explains a lot of this in detail.