"I do not know Julia."

Translation: Nie znam Julii.

[AdamMlodoz]

Any way to find out declensions of names? Or is it irregular?

[Vengir]

It has rules, but at first it might be a good idea to consult wiktionary: https://pl.wiktionary.org/wiki/Julia

PS: Declension of some foreign names is the most likely place you will see an apostrophe in Polish (although some people tend to overuse it).

[SpanPolielsh]

Does Polish differentiate between knowing and familiarity (e.g. Spanish saber vs. conocer)?

[Vengir]

There are basically two words for knowing in Polish "znać" and "wiedzieć". "Znać" is used with sentence objects without any additional words necessary. "Wiedzieć" is for clauses, when you kind of need to explain what you know, instead of just saying one thing.

For example:
Znam go – I know him
Wiem, gdzie poszedł – I know where he went

[RichlovesEU]

I don't understand the double 'i' for Julie?

[alik1989]

The first i is part the of the stem Julia and the second one is added to indicate the genitive.

[Jellei]

If it was "Nie znam Juli", then it would mean that her name is "Jula".

[dfwgator]

Nie będę Julią
https://www.youtube.com/watch?v=_c4nDF6amFA