Hello Traividya,
I am not sure of the exact solution to show only the month in English Language when the default language is German. Until you get a better answer from someone else, can you try this workaround.
Use custom Date Picker widget from the App Store and let users input the Month by typing the Month Number instead of selecting which takes care of the language part by eliminating language as it doesn’t involve showing the Month in MMM format and just the number in MM so that it takes care of the language?
I know this is not the answer you are looking for, still you can give a try before getting an answer that fits best