Learn Portuguese (Portugal): A televisão está estragada outra vez.

Even if the television seems permanently ruined, being broken is considered a physical condition or state in Portuguese, not an inherent characteristic. Because of this, you must use estar (used for states and conditions) rather than ser (used for essential traits).

Why is the word for "broken" estragada here? Could I use partida?

You use estragada (ruined, damaged, or malfunctioning) when referring to machines, electronics, or food going bad. If you used partida, it would imply the television was physically smashed into pieces! Notice it ends in "-a" to agree with the feminine noun a televisão.

Does outra vez literally translate to "again"?

Literally, it translates to "another time" (outra means another, and vez means time or instance). However, it is the most common and natural way to say "again" in everyday Portuguese in Portugal. You could also use the single word novamente to mean the exact same thing.