It's a shame when a film has a great idea but just can't manage to craft a solid entertainment from that idea. Here the filmmakers had several things going for them - a good idea, a good setting, amazing creature designs - but made the crippling choice to shoot the film in the now tired Found Footage style. This decision destroys any chance of the story coming together in a satisfying way. The first hurdle is the usual 'why is he still filming' question which is never well answered in the movie. The second problem is that such cameras as are used in this film would seem to be either anachronistic or so out of the ordinary as to be prohibitively expensive to be sent out with Russian soldiers in World War II.
As I said -a shame. Maybe one day a remake will find a good movie buried in this concept. They won't have to create more creatures but they will have to just shoot the thing as a proper film.