Learn Hardcore Portuguese (Brazil): Eles responderam que a nova conta estará pronta amanhã de manhã. - They answered that the new account will be ready tomorrow morning.

Responderam indicates that the act of answering is already completed. In Portuguese, you choose the tense based on when the action of speaking happened. They have already given their answer, so you use the past tense. Responderão would mean “they will answer” (i.e., the answering itself happens in the future).

Why does the second verb appear in the future tense as estará, even though responderam is in the past?

Portuguese allows the subordinate clause to keep its own time reference relative to the moment of speech. The readiness of the new account is still in the future from now, so you use the future indicative estará. It’s similar to saying in English: “They said the account will be ready tomorrow.”

What’s the function of que after responderam? Could we use responderam a instead?

Here que is a conjunction introducing reported speech: “they answered that …” If you say responderam a, you’re using the verb “responder” transitively: responderam à pergunta (“they answered the question”). But to report content, you need que: responderam que a nova conta…

Could we use the future subjunctive, as in que a conta estiver pronta, instead of the future indicative estará pronta?

No. The future subjunctive (e.g. estiver) expresses a condition or something uncertain: “when the account is ready.” In a factual statement about the future, you use the future indicative estará pronta because it’s a firm assertion, not a hypothetical or dependent clause of time/condition.

Why is estar used with pronta instead of ser? Can we say será pronta?

In Portuguese, estar describes a temporary state or condition, such as being ready. Pronto (“ready”) is a state resulting from preparation, so you say estar pronto. Será pronta would sound odd because ser implies an inherent characteristic, not a status change.

Why does the sentence say amanhã de manhã? Could we just say amanhã, or use amanhã pela manhã or amanhã cedo?

Amanhã alone means “tomorrow” without specifying time of day.
Amanhã de manhã is the most common colloquial way to say “tomorrow morning.”
Amanhã pela manhã is slightly more formal but identical in meaning.
Amanhã cedo (“early tomorrow”) is also possible, but it emphasizes “early” rather than the whole morning period.

Why is it a nova conta with the article a and adjective nova? What agreement rules apply?

Conta is a feminine noun in Portuguese, so it takes the feminine singular article a. The adjective nova also must agree in gender (feminine) and number (singular). If it were a masculine plural noun, you’d use os + adjective ending in -os, etc.

What does conta mean in this context? Does it always mean “account”?

Here conta refers to a bank or service account. However, conta can also mean “bill” or “check” in a restaurant, or simply “count” in mathematical contexts. You determine the meaning from context and accompanying verbs or qualifiers (e.g., conta bancária vs. conta no restaurante).