Learn Hardcore German: Bevor der Tag begann, hatten wir die Wolldecke schon auf das Sofa gelegt. - Before the day began, we had already put the wool blanket on the sofa.

In German, the Plusquamperfekt marks an action that happened before another past event. In the sentence, laying the blanket occurred before the day began (der Tag begann). To show this “past of the past,” German uses hatten (imperfect of haben) + past participle gelegt.

Could we say haben gelegt (Perfekt) or legten (Präteritum) instead?

Both forms are grammatically possible but change the nuance:

Perfekt (haben gelegt) is common in spoken German but doesn’t highlight the sequence as clearly.
Präteritum (legten) is typical in written narration but still doesn’t express “one past action before another.”
The Plusquamperfekt is the clearest way to show that the blanket was laid down before the day began.

Why is the verb begann at the end of the clause Bevor der Tag begann?

Bevor is a subordinating conjunction. In subordinate clauses introduced by words like bevor, the finite verb moves to the very end of that clause. Hence der Tag (subject) comes before and begann (verb) appears last.

After the subordinate clause, why does the main clause start with hatten instead of wir?

German main clauses follow the Verb-Second (V2) rule. When a subordinate clause like Bevor der Tag begann comes first, it occupies the “first position.” The main clause then must place the finite verb (hatten) in the next spot, followed by the subject (wir).

Why do we say auf das Sofa gelegt (accusative) and not auf dem Sofa gelegt (dative)?

The preposition auf can take accusative for a change of location (movement toward something) or dative for a static position. Here legen is a movement verb (“to lay onto”), so we use the accusative case: auf das Sofa.

What is the role of schon in hatten wir die Wolldecke schon auf das Sofa gelegt?

Schon means already and emphasizes that the action was completed before the reference point (the day’s beginning). It usually comes after the auxiliary verb (hatten) and before the main action phrase.

Can auf das be contracted here in colloquial German?

Yes. In spoken and informal contexts, auf das often becomes aufs:
Wir hatten die Wolldecke schon aufs Sofa gelegt.

Why is Wolldecke feminine and why do we use die?

Every German noun has a gender. Wolldecke (“wool blanket”) is feminine, so its definite article in both nominative and accusative is die. In this sentence, die Wolldecke is the direct object (accusative), so it remains die.