Antes de intercambiar ropa, descosemos el remiendo y enhebramos la aguja.

Antes de means before.

After antes de, Spanish normally uses an infinitive when the subject stays general or is the same idea as the main clause:

• Antes de salir = before leaving
• Antes de comer = before eating

So antes de intercambiar ropa means before exchanging clothes.

A useful contrast:

• Antes de + infinitive = before doing something
• Antes de que + subjunctive = before someone does something

For example:

• Antes de salir, cerramos la puerta.
• Antes de que salgas, cierra la puerta.

Because it comes after antes de.

In Spanish, prepositions such as de, para, sin, and por are often followed by the infinitive when English might use before doing, for doing, without doing, etc.

So:

• antes de intercambiar
• not antes de intercambiamos

That is a very common pattern in Spanish grammar.

They are both in the nosotros form, meaning we:

• descosemos = we unpick / we unstitch
• enhebramos = we thread

Spanish often leaves out subject pronouns when the verb ending already makes the subject clear. So you do not need nosotros here.

Compare:

• Nosotros descosemos el remiendo.
• Descosemos el remiendo.

Both mean the same thing. The second is more natural in many contexts.

Formally, enhebramos can be either:

• present: we thread
• preterite: we threaded

That happens with many -ar verbs in the nosotros form.

So the tense is decided by context. In this sentence, it is most naturally understood as present, especially if the sentence is describing a process, a general action, or instructions.

By contrast, descosemos is clearly present here, because the preterite of descoser would be descosimos.

Because ropa is being used in a general sense.

In Spanish, when talking about something in a general or non-specific way, the article is often omitted after certain verbs:

• comprar pan
• llevar sombrero
• intercambiar ropa

If you say la ropa, you usually mean specific clothing already identified in the conversation.

So:

• intercambiar ropa = exchange clothing / exchange clothes in general
• intercambiar la ropa = exchange the clothes, a specific set of clothes

Because ropa is a singular collective noun in Spanish.

English uses clothes, which is plural in form. Spanish usually uses ropa, which is grammatically singular but refers to clothing in general.

So:

• la ropa está limpia = the clothes are clean

Even though the meaning may refer to many items, the noun itself is singular.

The definite article usually points to something specific, identifiable, or already understood in the situation.

• el remiendo = the patch
• la aguja = the needle

This suggests we are talking about a particular patch and a particular needle relevant to the task.

Spanish also uses the definite article more often than English does in practical or familiar contexts. So la aguja can sound natural even where English might say a needle, depending on context.

If the objects were indefinite or new to the conversation, un remiendo or una aguja could also be possible.

Descoser means to unsew, to unstitch, or to unpick stitches.

It is built from:

• coser = to sew
• des- = a prefix that often gives the idea of undoing or reversing an action

So descoser el remiendo means to remove the stitching holding the patch in place.

It is more specific than just quitar. Quitar means to remove, but descoser tells you that the removal is done by undoing stitches.

Not usually.

Intercambiar normally means to exchange or swap. So intercambiar ropa suggests exchanging clothes, perhaps with another person or between outfits.

If you mean to change clothes in the everyday sense of putting on different clothes, Spanish more often says:

• cambiarse de ropa

So this sentence sounds more like a literal exchange/swap of clothing than the everyday idea of getting dressed in something else.

Because that opening part is an introductory phrase.

Spanish often uses a comma after a longer introductory phrase to make the sentence easier to read:

• Antes de intercambiar ropa, descosemos el remiendo...

The comma marks a pause and separates the setup from the main action.

In some short sentences, commas after introductory phrases can be omitted, but here the comma is natural and helpful.

No, Spanish word order is fairly flexible, but this is the most neutral order:

• verb + object
• descosemos el remiendo
• enhebramos la aguja

You could rearrange parts for emphasis, but the standard order is the most common and easiest for learners to follow.

For example:

• Enhebramos la aguja y descosemos el remiendo changes the sequence of actions.
• El remiendo lo descosemos... adds emphasis and sounds more marked.

So the original order is simply the most straightforward one.