Did Hitler also make big improvements during that year? And how did they compare?
He increased the size of his army quite dramatically - but a lot of that increase occurred in August 1939 with the mobilisation of the reserves, which would have happened in September 1938 if the war had started then.
Besides that, the size of the Navy (Kriegsmarine) and the Air Force (Luftwaffe) were increased as well, as more ships and planes came online, but far less dramatically than was the case in Britain. Germany was probably 60% along the way to war readiness in 1938, Britain was about 20% along the way. By September 1939, Germany was at about 90%, Britain at about 70%. That year made a lot more difference for the UK than it did for the Germans.