Learn German: Haben sie über das Projekt geredet? - Did they talk about the project?

Regular verbs usually form their past participle with ge- at the beginning and -t at the end. But because the stem of reden (to talk) ends in a 'd' (red-), we add an extra 'e' to make it easier to pronounce: ge-red-e-t. You will also see this with verb stems ending in 't', like arbeiten becoming gearbeitet.

Why is geredet at the very end of the sentence?

In German, the spoken past tense (the Perfekt) acts like a frame around the sentence. The helping verb (Haben) takes the first position to ask a yes/no question, and the past participle (geredet) is always pushed to the very end.

How do we know sie means 'they' and not 'she'?

We can tell by looking at the helping verb! If it were 'she', the verb would be conjugated as Hat sie (Has she). Because the verb is Haben (Have), sie must mean 'they'. It could also mean the formal 'you', but that would be capitalized as Sie.

Why do we use über for 'about' here?

The preposition über often means 'over' or 'above', but when used with verbs of communication like reden (to talk) or sprechen (to speak), it translates to 'about'. So über das Projekt means 'about the project'.