Nach dem Duschen wische ich das Waschbecken ab.

Because nach takes the dative case when it means after in a time expression.

So:

• nach
  • dative
• das Duschen becomes dem Duschen

That is why you get:

• nach dem Duschen = after showering / after the shower

In this sentence, Duschen is being used as a noun, not as a normal verb.

German often turns verbs into nouns this way:

• duschen = to shower
• das Duschen = showering / the act of showering

All nouns are capitalized in German, so it becomes Duschen with a capital D.

Because after nach in this kind of expression, German normally uses a noun phrase, not a bare infinitive.

So German says:

• nach dem Duschen = after showering

not:

• nach duschen ❌

If you want to use a full verb clause instead, you could say:

• Nachdem ich geduscht habe, wische ich das Waschbecken ab.

That means essentially the same thing.

German main clauses usually follow the verb-second (V2) rule.

That means the finite verb must come in the second position, no matter what comes first.

Here the first element is:

• Nach dem Duschen

So the finite verb must come next:

• wische

Then comes the subject:

• ich

So:

• Nach dem Duschen | wische | ich | das Waschbecken ab

This is very normal German word order.

Because once Nach dem Duschen is placed first, the verb still has to stay in second position.

So the order becomes:

• first element: Nach dem Duschen
• second position: wische
• then the subject: ich

Compare:

• Ich wische nach dem Duschen das Waschbecken ab.
• Nach dem Duschen wische ich das Waschbecken ab.

Both are correct. The second version emphasizes the time expression a bit more.

Because abwischen is a separable verb.

Its basic form is:

• abwischen = to wipe off / wipe down

In a main clause, the prefix separates:

• Ich wische das Waschbecken ab.

So:

• wische = the main verb part
• ab = the separated prefix, placed at the end

This is very common in German with separable verbs.

Abwischen means to wipe off, to wipe down, or to wipe clean, depending on context.

In this sentence:

• das Waschbecken abwischen

means something like:

• to wipe down the sink
• to wipe the sink off

It suggests cleaning away water, toothpaste, soap, etc.

Because das Waschbecken is the direct object of abwischen, so it is in the accusative case.

The noun Waschbecken is neuter:

• nominative: das Waschbecken
• accusative: das Waschbecken

For neuter nouns, nominative and accusative look the same, so the form does not change.

Yes. That is also correct.

Both of these are grammatical:

• Nach dem Duschen wische ich das Waschbecken ab.
• Ich wische nach dem Duschen das Waschbecken ab.

The difference is mainly focus:

• Nach dem Duschen ... puts the time expression first
• Ich ... starts more neutrally with the subject

Not exactly.

• nach dem Duschen = after showering / after the act of showering
• nach der Dusche = after the shower

Sometimes they can be similar in meaning, but nach dem Duschen is the more natural way to talk about after taking a shower.

Using the nominalized verb Duschen focuses on the activity itself.

Yes.

A more explicit version would be:

• Nachdem ich geduscht habe, wische ich das Waschbecken ab.

This means:

• After I have showered, I wipe down the sink.

Difference:

• nach dem Duschen = shorter, more compact
• nachdem ich geduscht habe = full subordinate clause

Both are common.

Because German simple present often covers meanings that English expresses in different ways.

• Ich wische das Waschbecken ab can mean:
  • I wipe down the sink
  • I am wiping down the sink (depending on context)
  • I do wipe down the sink (with emphasis)

German does not need an extra helping verb like English often does.

It could be either. The present tense in German is often flexible.

Depending on context, it might mean:

• After showering, I wipe down the sink. → a habit
• After showering, I’m wiping down the sink. → what I’m doing now
• After I shower, I wipe down the sink. → routine

The sentence itself does not force only one interpretation. Context decides.