Wir erweitern das Netzwerk erst, wenn alle Voraussetzungen geprüft worden sind.

We will expand the network only when all prerequisites have been checked.

Breakdown of Wir erweitern das Netzwerk erst, wenn alle Voraussetzungen geprüft worden sind.

• wir: we
• wenn: when
• alle: all
• erst: only
• das Netzwerk: the network
• die Voraussetzung: the prerequisite
• erweitern: to expand
• geprüft worden sein: to have been checked

Questions & Answers about Wir erweitern das Netzwerk erst, wenn alle Voraussetzungen geprüft worden sind.

Why is erst used here, and what exactly does it emphasize?

erst signals that the action in the main clause happens only after the action in the subordinate clause is fully completed. In English it’s like saying “only once” or “not until.”

What does the conjunction wenn mean in this context? Could I use als or weil instead?

Here wenn introduces a temporal subordinate clause meaning “when” or “once.”

• als refers to a single event in the past and can’t express a general or future-conditioned timing.
• weil means “because” (giving a reason), not “when.”

Why does the subordinate clause end with geprüft worden sind? How is that constructed?

This is the present perfect passive in a subordinate clause. It breaks down as:

• geprüft = past participle of prüfen
• worden = past participle of werden (the passive marker)
• sind = present tense of sein (auxiliary for perfect passive)
  Plus, subordinate clauses push all verb parts to the very end, so you get geprüft worden sind.

Could I say wenn alle Voraussetzungen geprüft werden instead? What’s the difference?

You could use the present passive (geprüft werden), but that implies a general or ongoing action (“when they are being checked”). The perfect passive (geprüft worden sind) makes it clear the checking is finished before the expansion takes place.

Why is das Netzwerk in the accusative case here?

Because das Netzwerk is the direct object of the transitive verb erweitern (“to expand/extend”). In German, direct objects take the accusative.

What case is alle Voraussetzungen in the subordinate clause, and why does it look like the accusative?

In the passive clause alle Voraussetzungen functions as the subject (nominative plural). In German passive, the former object of the active verb becomes the subject. Since alle + plural noun has the same form in nominative and accusative, it appears unchanged.

Can I move Erst wenn alle Voraussetzungen geprüft worden sind to the front? What changes in word order?

Yes. Placing the erst wenn-clause first counts as a fronted element, so the main clause inverts: the finite verb appears immediately after the comma, then the subject. For example:
Erst wenn alle Voraussetzungen geprüft worden sind, erweitern wir das Netzwerk.