Learn Portuguese (Portugal): Deduzir a resposta da charada foi péssimo. - Deducing the answer to the riddle was terrible.

péssimo is the irregular absolute superlative of mau (bad). Instead of saying muito mau (very bad), Portuguese often uses péssimo to express something that is exceptionally bad, terrible, or awful. It elevates the intensity of the adjective without needing an adverb like muito.

Both resposta and charada are feminine nouns. Why is the adjective péssimo in the masculine singular form?

The adjective péssimo is not describing the riddle (charada) or the answer (resposta). It describes the whole action of deducing it (Deduzir a resposta da charada). When an adjective characterizes a verb in the infinitive or an entire clause, it always takes the default masculine singular form.

The English translation says 'answer to the riddle'. Why does the Portuguese use da instead of à?

In English, we often say the answer to a question or a riddle. In Portuguese, possession is used instead. You refer to the answer of the riddle, so it becomes a resposta da charada (combining the preposition de with the feminine article a).

Why use foi (from ser) instead of esteve (from estar) to describe how the experience felt?

When evaluating an event, an action, or a fact as an abstract concept, Portuguese typically uses ser. The speaker is categorizing the entire act of deducing the riddle as a definitively terrible thing, rather than describing a temporary physical or emotional state.