"The nights are hard and ugly."

Translation: Nopțile sunt grele și urâte.

[RowanM.1]

Romanian night life sounds kind of depressing.

[Chasavaqe]

I think you mean "The night is dark and full of terrors"

[FilipFilip17]

What a lovely sentence.

[AlphaMale2099]

Why "grele" instead of greu or grea?

[RowanM.1]

The adjective is agreeing with the plural noun. Greu or grea would be agreeing with singular masculine or feminine nouns. Romanian adjectives, like adjectives in other Romance languages, change according to both the gender and number of the noun they modify.