The movie claims to be inspired by true events, but it's likely that some details were fictionalized or dramatized to make it more engaging for the audience. So, it's not a completely accurate account of what happened in reality.
It's based on real events, but there might be some artistic liberties taken for the sake of the narrative.
The Devils Double has elements of truth, but like many films based on real-life, it's a blend of facts and creative interpretation. It gives a portrayal that's supposed to be close to the real story, but there's no guarantee of 100% authenticity.