Sobald die Nudeln fertig sind, gieße ich sie im Sieb ab.

Sobald means as soon as.

So Sobald die Nudeln fertig sind means as soon as the noodles are ready.

Compared with wenn:

• sobald = as soon as, with a stronger sense of immediacy
• wenn = when / whenever / if, depending on context

So:

• Sobald die Nudeln fertig sind, ... = the next action happens immediately after they are done
• Wenn die Nudeln fertig sind, ... = when the noodles are ready, ..., which is a bit more neutral

Both can work, but sobald is more precise here.

Because Sobald die Nudeln fertig sind is a subordinate clause.

In German, when a clause begins with a subordinating conjunction like:

• sobald
• weil
• dass
• wenn
• obwohl

the conjugated verb goes to the end of that clause.

So:

• die Nudeln sind fertig = main clause word order
• sobald die Nudeln fertig sind = subordinate clause word order

That is why sind comes last.

Because the sentence starts with a subordinate clause, and in German that clause is separated from the main clause by a comma.

So the structure is:

• Sobald die Nudeln fertig sind, = subordinate clause
• gieße ich sie im Sieb ab. = main clause

German uses commas with subordinate clauses much more consistently than English does, so this comma is required.

This is because the subordinate clause comes first.

In German main clauses, the finite verb must be in second position. If something other than the subject comes first, the verb still stays second.

Here, the whole first position is taken by:

• Sobald die Nudeln fertig sind

So the main clause must begin:

• gieße ich ...

not:

• ich gieße ...

Compare:

• Ich gieße sie im Sieb ab.
• Sobald die Nudeln fertig sind, gieße ich sie im Sieb ab.

This is a very common German pattern.

Abgießen is a separable verb. It means to drain off, to pour off, or in cooking context to drain.

In a normal present-tense main clause, separable verbs split apart:

• Ich gieße die Nudeln ab.
• Er gießt das Wasser ab.

So:

• gieße = the conjugated verb part
• ab = the separable prefix, placed at the end

But in an infinitive or subordinate-clause verb form, it stays together:

• die Nudeln abgießen
• weil ich die Nudeln abgieße
  Actually here in a subordinate clause with a conjugated form, it becomes abgieße as one word at the end.

So in your sentence, gieße ... ab is exactly what you expect from a separable verb in a main clause.

Yes. Here sie means them, referring back to die Nudeln.

Because die Nudeln is plural, the matching pronoun is sie.

So:

• die Nudeln = the noodles
• sie = them

This can be confusing because sie can also mean:

• she
• they
• you (formal, written Sie)

But here the meaning is clearly them because it refers to die Nudeln.

German often uses the definite article more than English does.

So die Nudeln can mean:

• the noodles
• or, in context, simply the pasta / the noodles I’m cooking

In English, we often leave out the article more easily, but in German it is very normal to include it.

You could sometimes say just Nudeln, depending on context, but die Nudeln sounds completely natural here because we are talking about a specific batch of noodles.

Fertig usually means finished, ready, or done.

With food, it often means:

• done
• ready
• cooked

So die Nudeln sind fertig means the noodles are done cooking and ready for the next step.

Very common examples:

• Das Essen ist fertig. = The food is ready.
• Ich bin fertig. = I’m finished / done.
• Bist du fertig? = Are you done?

Im Sieb means in the colander / in the sieve.

It is a contraction of:

• in dem Sieb → im Sieb

This contraction is very common:

• im Haus = in dem Haus
• im Wasser = in dem Wasser
• im Sieb = in dem Sieb

In this cooking context, Sieb usually means a sieve or colander.

Because the sentence is describing where the noodles are drained: in the colander.

• im Sieb = in the colander
• mit dem Sieb = with the colander

Both are grammatically possible in different situations, but they mean slightly different things.

Here, im Sieb abgießen is the natural way to express draining something by putting it into a sieve/colander.

So the focus is not really the tool as an instrument, but the place/container where the draining happens.

Because in can take either:

• dative for location
• accusative for movement toward a destination

Here, the phrase describes the draining as happening in the colander, so German uses dative:

• in dem Sieb → im Sieb

And Sieb is a neuter noun:

• das Sieb

Its dative singular form is:

• dem Sieb

So:

• das Sieb = nominative/accusative
• dem Sieb = dative
• im Sieb = in dem Sieb

The full verb here is abgießen, not just gießen.

• gießen by itself usually means to pour
• abgießen means to pour off / drain

So for pasta, potatoes, or anything where you remove the water, abgießen is the useful cooking verb.

Examples:

• Ich gieße das Wasser ab. = I pour off the water.
• Kannst du die Kartoffeln abgießen? = Can you drain the potatoes?

Because the infinitive is gießen.

In standard German spelling, ß is used after a long vowel or diphthong in many words, and the ie in gießen is a long vowel sound.

So:

• gießen
• ich gieße
• du gießt
• er/sie/es gießt

In Swiss German spelling, you may see ss instead of ß, so giesse can appear in Swiss texts. But in standard German used in Germany and Austria, gieße is the normal spelling.

No, that is not correct standard German.

After the initial subordinate clause, the main clause still follows the verb-second rule. Since the first position is already occupied by the whole sobald clause, the verb must come next:

• Sobald die Nudeln fertig sind, gieße ich sie im Sieb ab.

Not:

• Sobald die Nudeln fertig sind, ich gieße sie ...

This is one of the most important German word-order rules to get used to.

Yes. In everyday German, Nudeln is often used broadly for what English speakers might call either noodles or pasta, depending on the type.

So in a cooking sentence like this, die Nudeln could mean pasta noodles in general.

The exact English translation depends on context, but the German word itself is perfectly normal here.

Yes, it sounds natural.

It has several very typical features of everyday German:

• Sobald for as soon as
• subordinate clause verb at the end: fertig sind
• main clause verb-second order: gieße ich
• separable verb: gieße ... ab
• common contraction: im Sieb

A native speaker might also say similar versions such as:

• Wenn die Nudeln fertig sind, gieße ich sie im Sieb ab.
• Sobald die Nudeln fertig sind, gieße ich das Wasser ab.
• Sobald die Nudeln gar sind, gieße ich sie ab.

But your sentence is fully natural and idiomatic.