Fatih Akin doesn't need to prove he knows how to direct or that he is a capable director. But if you need another example here it is. One might say he gets back to his roots or rather his first film somewhat with this. But with the spin that he concentrates on the female perspective. You could also argue that the male might come from that world he created with his first movie (which some may argue is his "Mean Streets" - except he didn't stay in that genre).
Diane Kruger is really exceptional in this and very close to real life. So you won't see any over the top and unbelievable stuff happening here. And it all leads to an ending that will either satisfy you or leave quite empty and maybe annoyed. It is tough to please everyone of course, but if you like slow burning drama with thriller elements in it, this is really good. Devastating and painful, but good ...