Learn Italian: Ho perso di nuovo le chiavi.

Yes, you can! Ho perso ancora le chiavi is also correct and means "I lost my keys again." Di nuovo (literally "of new") is a very common phrase used just like an adverb of frequency to mean "again" or "anew."

Why is di nuovo placed before le chiavi? Can I put it at the end of the sentence?

You have some flexibility! In Italian, adverbs of time and frequency often go right after the verb, which is why di nuovo sits between ho perso (I lost) and le chiavi (the keys). However, saying Ho perso le chiavi di nuovo at the end of the sentence is also perfectly fine and sounds very natural.

Is perso an irregular verb form?

Yes, perso is the irregular past participle of the verb perdere (to lose). Instead of following the regular -uto ending pattern for -ere verbs, it changes to perso. Combined with ho (I have), it makes the past tense ho perso (I lost / I have lost).

The translation says "my keys," but the Italian just says le chiavi (the keys). Why is there no word for "my"?