"If he is drinking, I am eating."

Translation: Jeśli on pije, ja jem.

[iamZemmi]

I wrote "jeśli on pije, jem" - why is "ja" important here? Is it for emphasis?

[israellai]

Because you're mentioning two different persons here, so we need the stronger contrast to clarify things.

[akbargumbira]

yes me too. The subject is kind of redundant no?

[immery]

Emphasis here is important, we have contrast between subjects. If we have a sentence with two subjects, those need to be said, especially second one.
Jem, on pije - Ok
Antek does something. Pije, ja jem. - ok
Ja jem ,on pije/ On pije , ja jem ok, more accent put on contrest between subjects

[akbargumbira]

Bardzo jasno! Thanks

[deactivated user]

What is the difference between "jeśli" and "jeżeli"?

[Jellei]

Almost none. "Jeżeli" is a bit rarer and a bit more official.

[deactivated user]

Thanks! (And since you are now on level 15 in Russian, I can tell you that "yezheli" also exists in Russian, but it sounds fancy, poetic, and outdated)

[ETS2143]

It's the same :D

[Rafkens]

Jak on pije, ja jem - should be also correct.

[Jellei]

Makes sense to me, added.