The structure for History essays are unlike those in Economics or Geography, however it is similar to many literature subjects. *FYI, i don't do Hitler and WW2 for History. Some facts may be wrong.*
First, start with a strong introduction. Specify the country, leader, time period etc to make sure the examiner knows immediately what you are going to talk about. Often, it is recommended for struggling students to rewrite the question as a statement. (For example: To what extent was propaganda a significant in the rise of totalitarian power in one European country in the years 1920 to 1945? -> Hitler rose to power in Weimar Germany starting from the 1920s and eventually became the Fuhrer in 1934. Propaganda played a significant role in creating disillusionment with the Weimar Government, allowing him to rise to power. However, other factors such as the Great Depression, the Treaty of Versailles and post-war conditions also played a significant role in his rise to power.) As you can see in the example, I answer the question explicitly, clearly stating who, where, what and when I am writing about. Stating what you are going to talk about helps structure your essay as well. Seen in the example, you then can start with propaganda, then the Great Depression, ToV and post-war conditions in that order. This will gain your organisation and answer coherent marks.
Second, always use statistics and perspectives. Use specific examples of Hitler's Germany like casualty numbers, the number of people who can vote, economic statistics, tax rates, people's wages etc. To avoid overloading information in your head, memorise statistics and perspectives that can be used in different questions and not just one. If you forgot a specific number, you can substitute with vague information. (For example: instead of only 6% of people being able to vote, you can substitute with "less than 10%" or "approximately 5%") This way you still have statistics and it isn't wrong. Just don't be too vague. In terms of historical perspectives, don't panic if you don't remember who said it or the exact quote. (For example: if you forgot who the historian is, state "a post-revisionist economic historian focusing on the effects of economy on support for Hitler" or if you forgot the quote, state instead the general idea of the quote "XXX believes that Hitler's rise to power was mainly due to the failure of the Weimar Republic.) However, these examples are not recommended and should only be used when absolutely necessary. When you use any statistics or perspectives, don't just state it, say what this means, how does it contribute to your thesis etc. (For example: Only 6% of the population can vote in elections. This lack of political rights of the population enables Hitler to suppress the population and pass laws that only strengthened his position in power. Furthermore, this 6% of population were mainly Nazi Party members. This allows the elections to be biased for the party and not for the interest of the overall population, enabling pro-party policies that squashed other party powers and consolidate Hitler's power) Do not just put in statistics and perspectives for the sake of having it and do not not put any. Aim for 3~4 statistics and 2~3 perspectives in your next essay. Get teacher feedback and try to add some more. You should have 5~6 statistics and 4~5 perspectives in your essay, if possible and if you are lucky enough to memorise enough that can be used in your essay. If not, the early mentioned 3~4 statistics and 4~5 perspectives is enough.
Third, paper 2 and paper 3 are different in writing styles. You can be a little more generic and broad in paper 2 arguments and content while paper 3 requires a more detailed content. So, study up more on paper 3, especially when there are 3 essays for it.
Finally, end you essay with something similar with your intro, stress on similar.Your ending should not be the same as your intro. Rephrase it and use some evidence you mentioned in your essay to back up your thesis again in the end. Do not mention anything new in the end.
Good luck in your future History exams. :3