The French title of this movie says "do you good" rather than "help". A better title, I think, since Harry is a do-gooder, in the worst sense of the term.
This movie is about this guy called Michel, a famous writer with several years of writer's block. One hot day, in the middle of nowhere, a stranger buys Michel a drink, and then quotes one of the poems that Michel wrote when they were at school together, and says how sorry he is that Michel hasn't written anything recently, and he'd like to help....
The help that Harry offers Michel takes many forms, some of it quite illegal. I could describe this as a black comedy. Reminiscent of Ronin perhaps, with people getting killed without anyone being too bothered, but more definitely lots of mysterious events which you have to explain as "Harry's helping". Filmed largely in Argentina because France doesn't have anywhere in the middle of nowhere.