Learn Hardcore German: Wenn wir an der Schule vorbeigehen, sehen wir sofort den Park. - When we walk past the school, we immediately see the park.

Because wenn is a subordinating conjunction. In subordinate clauses, the finite verb goes to the end. With a separable verb like vorbeigehen, the prefix stays attached at the end in subordinate position: wenn wir an der Schule vorbeigehen.

Why does the second clause begin with sehen?

German main clauses are verb-second. The whole wenn-clause counts as position 1, so the finite verb of the main clause must come next: …, sehen wir … (inversion of verb and subject).

Do I need the comma?

Yes. Subordinate clauses are always set off by a comma: Wenn …, sehen …. If you put the main clause first, you still use a comma: Wir sehen …, wenn ….

Why is it an der Schule and not an die Schule?

With vorbeigehen, the fixed pattern is an + dative to mark what you pass by. die Schule is feminine; dative is der, hence an der Schule. an + accusative would indicate motion toward a destination, which is not the meaning here.

Is vorbeigehen a separable verb? Where does vorbei go?

Yes.

Main clause (present): Wir gehen an der Schule vorbei.
Subordinate clause: …, dass wir an der Schule vorbeigehen.
Perfect: Wir sind an der Schule vorbeigegangen.
Future: Wir werden an der Schule vorbeigehen.

Can I reverse the order of the clauses?

Yes: Wir sehen sofort den Park, wenn wir an der Schule vorbeigehen. Meaning and grammar stay the same (comma required).

What cases are used here, and why den Park and der Schule?

wir: nominative subject.
den Park: accusative masculine (direct object of sehen; nominative would be der Park, accusative is den Park).
an der Schule: dative feminine after an with vorbeigehen.

Where can I put sofort? Is Wir sehen den Park sofort also correct?

Both Wir sehen sofort den Park and Wir sehen den Park sofort are natural. Word order in the middle field is flexible; putting sofort earlier can highlight the immediacy a bit more, but there’s no change in core meaning.

Why wenn here and not als or wann?

wenn: “when(ever)” for general/habitual time or conditions, also “if.”
als: one-time event in the past.
wann: question word (“when?”), used in direct or indirect questions, not as a conjunction here.

Could I use sobald instead?

Yes: Sobald wir an der Schule vorbeigehen, sehen wir den Park. It compresses the idea of “as soon as … we immediately see …” into one conjunction.

Does bei der Schule work here?

Not for “walk past.” Use an der Schule vorbeigehen. bei der Schule means “near/at the school.” With verbs like vorbeikommen/ -fahren/ -gehen, bei can mean “stop by (at someone’s place),” which is a different idea.

Why not am Schule?

am = an dem. Schule is feminine; dative feminine is der, not dem. So it must be an der Schule. With a masculine noun you could say am Park (from an dem Park).

What’s the difference between an der Schule and in der Schule?

an der Schule: at/by the school (outside, adjacent area). Works with vorbeigehen to mean passing the outside.
in der Schule: inside the school building. in der Schule vorbeigehen would be odd here.

Is vorübergehen a valid alternative to vorbeigehen?

Yes, but it sounds more formal/literary. It can also mean “to pass (away), to elapse” when talking about time or symptoms. Everyday speech prefers vorbeigehen for “walk past.”

How do I negate this? Where does nicht go?

Negate the immediacy: …, sehen wir den Park nicht sofort.
Negate the seeing at all: …, sehen wir den Park nicht.
Negate the condition: Wenn wir nicht an der Schule vorbeigehen, sehen wir den Park nicht.

Can I replace an der Schule with a da- pronoun?

Yes: Wenn wir daran vorbeigehen, … (daran = “at/on it”). In colloquial speech you’ll also hear dran: Wenn wir dran vorbeigehen, ….