"Zsuzsa is painting new ones."

Translation: Zsuzsa újakat fest.

[Luzibr]

Why not festeni this time?

[jsiehler]

Festeni is the infinitive. In this sentence you need the third personal singular form, fest.

You would use the infinitive together with some other verb, like Zsuzsa újakat akar festeni, "Zsuzsa wants to paint new ones." In that sentence, akar is the "main" verb of the sentence and takes the 3rd person conjugation; festeni is used in the infinitive form.

[Kari712]

What about "Zsuzsa fest újakat"? Would that be incorrect or just change the emphasis and translate to something like "It is ZSUZSA who is painting new ones"?

[MrtonPolgr]

It's grammatical, just a rare thing to say. (I'm not sure whether that matters on Duolingo at all...)