I'm doing History as well, but not Nazi Germany but im guessing that the marks fo each question on my paper is quite similar to your paper.
For example, im guessing the 4mark question is something like "Describe a key feature.." of something, right? Well in this case, you would you need give one point and state how this made relations better or worse (It's about international relations right?)
And yeah, same for the 6 marks, but its more of giving more than one point and writing if relations got better or worse.
And finally for the 12 mark question, does your exam paper give you a time period and you choose the events that happened within? If so, basically choose 3 events (which were effective) and explain them; In school we were taught to do Cause, Event, Consequence then make a judgement on which event was the most effective. And to gain maybe an extra mark or 2 its better if you do a introduction and conclusion to the 12mark essay and use key words in it as well!