QUALCOSA is, according to italianGrammar, an indefinite pronoun. It comes from “qualche cosa” and it indicates in some non-specific way one or more things.

0 – QUALCOSA NUOVO, QUALCOSA NUOVA
These two probably represent the most common mistakes, from beginners to advanced learners. Indeed, both expressions are not correct.

In Italian, the pronoun QUALCOSA is never ever directly followed by an adjective. NEVER!

So, what do we do?

The correct way to build this type of sentences is:

QUALCOSA + preposition DI + masculine singular form of the adjective, always

Examples:

Qualcosa di nuovo —> La mia vita è abbastanza tranquilla: non succede mai qualcosa di nuovo.
(Something/nothing new —> I lead a pretty quiet living: nothing new ever happens.)

Qualcosa di buono —> C’è qualcosa di buono da mangiare in frigo?