How was it with/by you?

How's by you? is a word-for-word translation from Yiddish, and probably a German format.

Better English: How are things over on your side? What's doing in your life? How are you?

With the heavy immigrations at the turn of the century of Jews from Eastern Europe (say, Poland) to New York City, their language influence soon showed up in all NY speech. Yiddish is in fact its own melting pot, blending bits of handy expressions right in: Bubbie/granny is Polish. Pareve (neither meat or dairy, also bland) is Polish for steamed. Schmatta/rag is Polish.

Allan Sherman sang: How's by you?

The Andrew Sisters sang Bei Mir Bistu Shein. And by "By me", they meant To me, you're pretty great!

Again with the prepositions? Remember that prepositions from one language don't easily map to the next. Translations of idioms are naturally the worst. Like plaid and polka dot in the schmatte business, they're ongepotchket, let me tell you.