Watch some documentaries that were not produced by Americans and see how things differ.
Here is one on the Spitfire, one of the easiest to build and best defense aircraft of the war, it did not have the range to reach Germany but it did not have to.
https://www.youtube.com/watch?v=vDzZnCkbxgs
Here is one on the Canadian Navy, the third largest navy in the world at the end of the world with 90000 personnel.
https://www.youtube.com/watch?v=FOHQHF34ORQ
If you want to talk about the reason for the failure of the German war effort you can look East, the eastern front was a major contributor to the downfall of the German army. If Hitler kept his pact with Stalin the outcome of the war would have been much different.