I have always wondered ,if you don't speak the language how can you know how good a translation is? if I was translating something into Dutch for example I would not know if it was correct, it could be a load of nonsense for all I know.
Let's say you're chatting to your French mates and are wondering if they're suffering with the same wind and rain and floods that we are over here. You might ask "How's the weather over there?" Reasonable? You understand that perfectly. But ask Google translate to render that in French and you get "Comment est-il plus de temps?" You might remember from your school French that "comment" means "how" and "temps" means "weather", so off you blithely go! :-)
jeffa, no, the problem is as berniecuddles says: he gets stuff he understands and stuff that's nonsense.
You could try the alternatives suggested and see if they come up with something coherent, but translating moderately slangy street speech is often tricky even for people.