Like hindi and urdu, the biggest difference between yiddish and other german dialects is the script[1]. I have "Velo" and "Poulet", so my loan words are not as exotic as the hebrew/aramaic ("tukhes") and eastern european ("ну") influences on yiddish, but all the dialects[2] have loan words ("Homeoffice") and most have their own unique terms ("Rundumeli").

https://yi.wikipedia.org/wiki/הויפט_זייט is interesting if you can read hebrew script.

https://als.wikipedia.org/wiki/Wikipedia:Houptsyte_(Schwyzer... will give you some idea why I recommended starting with the NZZ, which almost writes in standardised german.

[1] it was yiddish that got me into russian, because it's easier to find more than just Andrews Sisters on YouTube in cyrillic: eg https://www.youtube.com/watch?v=JWeqbs9OFX0

also recommended, for any germanophone: https://www.youtube.com/watch?v=XH1fERC_504 (or anglophones who don't mind subtitles)

[2] in tourist hiking areas, a popular past-time is to guess where people are from by how they greet on the trail.

The difference between High German and Yiddish is much larger than between Urdu and Hindi.

He grew up in a multilingual environment, 'his original language' is not a very specific thing. He was educated in German, his family was of a social standing in which German was essential. They also spoke a variant of Yiddish - itself a (give or take) German dialect.

He was also totally fluent in Czech.

I'm glad, though, that he wrote in German. It's always nice to read authors in their original language.