Google translate works amazingly will on languages with a similar grammar (or at least, it works so on European languages, which I have the experience to judge).
However, translation of more distant languages is pretty terrible. Vietnamese to English is something I use Google translate for everyday and it's a mess. I can usually guess what the intended meaning was but if you're translating a paragraph or more it won't even be able to translate the same important subject words consistently throughout. Throw in any kind of slang or abbreviations (which Vietnamese people use a lot when messaging each other) and it's completely lost.
However, translation of more distant languages is pretty terrible. Vietnamese to English is something I use Google translate for everyday and it's a mess. I can usually guess what the intended meaning was but if you're translating a paragraph or more it won't even be able to translate the same important subject words consistently throughout. Throw in any kind of slang or abbreviations (which Vietnamese people use a lot when messaging each other) and it's completely lost.