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.

Breakdown of Eles responderam que a nova conta estará pronta amanhã de manhã.

What tense is responderam?

Responderam is the 3rd person plural preterite of responder.

The preterite is used here because it refers to a completed action in the past: they already gave that answer.

Why is eles used? Could Portuguese leave it out?

Yes. Portuguese often drops subject pronouns when the verb ending already makes the subject clear.

So both of these are possible:

The version with eles may be used for:

What is que doing in this sentence?

Here que means that and introduces a subordinate clause:

It connects the reporting verb (responderam) to what was said.

This is very common in Portuguese after verbs like:

Why is it estará and not ?