You know what I mean.

No, I don't. Early jewish communities in Central Europe spoke the local language, then carried this language with them as they moved into Eastern Europe and the Baltics. Over centuries it diverged from its ancestral origin, as all languages do. At no point did anyone look at another jewish language and go “oh that's interesting; let's do something like that.”

I have a hunch that Jews came from Eastern Europe (I mean Israel before that). No, I don't think they are Khazars. But Ashkenaz was in Scythia, i.e. Eastern Europe.

Their history is very well documented. The Ashkenazi came from Italy into Germany, then moved into Poland (a bit different geographically from modern day Poland) after crusader pogroms in the 11th century.

Jews were in Czech Republic since at least 9th century. I don’t think they were German Jews.

As I said, geography was a bit different back then. These are the same people I’m talking about. They came from Italy.

I don’t think they did but I won’t convince you.

I think that's a genuine dispute, because people consciously deciding to make a new language is a relatively rare phenomenon. Most language change is informal and unplanned.