If you think of this movie as Sci-Fi, it is a mess.
Let go the Sci part, and look at it for what it is. Fiction or just plain Fantasy.
The issue is that the script itself doesn't decide what this is. Time Travel or Parallel universes. If they don't understand the difference, explains why everything happened how it did.
Now.. it is not total garbage. As the pro list, i could say it was fun, characters are likable, and the FX is decent. The con list would be that the story/dialogue is borderline stupid (honestly, you will guess every single plot twist before it even start), and the acting ability is amateurish. So, if you watch this not expecting a mind bending movie, you might enjoy it. (Hey, there are some hollywood movies about the same topic that are completely moronic... )