There is one issue that is also for German native speakers
quite difficult; the thing with the double negation.
Often heard - at least in movies is:
I didn't do nothing. This
means that this person wants to say I didn't
do anything. or I did
To say I didn't do nothing
(or I ain't doing nothing) does not really get great
points for style, still is clear that this is a negative
sentence and it's clear what it means.
Now let's look at the German way.
The Germans use the mathematics for their negation which
means that two minuses makes a plus => two negations
make a positive sentence.
did not do
nothing = Ich
Ich habe nicht
= I did something.
Does this sound illogic to you? Well, it only tells you
to be careful how many negations you put in a sentence,
because the mathematical system is continued. Three
negations make it negative again, four make it positive
etc. My advice: just stick to one negation, that's the
easiest and understandable way also for German.
This principle of double negation
also works with the general negative words like
nobody = niemand
Again the English can be still understood as a negative
sentence even though we have to admit that it doesn't
sound so nice. Just for demonstrating purposes:
The German sentences gives the association that if
nobody said nothing, then all were saying everything.
This actually doesn't make much sense. Still that's
the way it goes.
Anyway the English grammar works actually the same.
If there is Nobody, No one, None in a sentence there
is no extra negation. The correct English would say:
Nobody said anything. = Niemand sagte etwas. And we
are in clear waters again.
The only useful general advice we can give it: stay
away from double negations - they are really confusing
to everybody in any conversation.