Når jeg kommer hjem, legger jeg nøkkelknippet på benken.

Because hjem and hjemme are used differently in Norwegian:

• hjem = home as a direction, when you are moving toward home
• hjemme = at home, when you are already there

So:

• Jeg kommer hjem = I come/get home
• Jeg er hjemme = I am at home

In this sentence, the speaker is describing movement toward home, so hjem is correct.

Norwegian often uses the present tense for things that happen regularly, generally, or in the near future. This sentence sounds like a habitual action:

• Når jeg kommer hjem, legger jeg nøkkelknippet på benken.
• When I get home, I put the keychain on the bench/counter.

So kommer is not necessarily talking about right now. It can describe what usually happens whenever the speaker gets home.

English does something similar:

• When I get home, I put my keys on the counter.

So the present tense here is very natural.

This is because of Norwegian word order. Norwegian is a V2 language, which means the finite verb usually comes in second position in a main clause.

The sentence begins with a subordinate clause:

• Når jeg kommer hjem, ...

After that, the main clause starts, and because something has been placed before it, the verb comes before the subject:

• legger jeg nøkkelknippet på benken

So:

• Jeg legger nøkkelknippet på benken. = normal word order
• Når jeg kommer hjem, legger jeg nøkkelknippet på benken. = inversion after the opening clause

This is very common in Norwegian.

Here, når means when and introduces a time clause.

In this sentence, it has the sense of whenever/when:

• Når jeg kommer hjem = When I get home

It often introduces something that happens regularly or as a general pattern. If the speaker is describing a routine, når is exactly what you would expect.

The ending -et makes the noun definite.

• et nøkkelknippe = a bunch of keys / a keychain / a key ring
• nøkkelknippet = the bunch of keys / the keychain

Norwegian usually adds definiteness to the end of the noun rather than using a separate word like the.

So nøkkelknippet means the specific keychain or bunch of keys the speaker has in mind, probably their own.

Yes. Norwegian makes very frequent use of compound nouns.

nøkkelknippet comes from:

• nøkkel = key
• knippe = bundle / bunch

Together:

• nøkkelknippe = bunch of keys / keychain
• nøkkelknippet = the bunch of keys / the keychain

Compound words are extremely common in Norwegian, much more so than in English spelling.

Yes, but legger is a very natural choice here.

å legge is often used when you lay something down, especially on a surface.

• Jeg legger boka på bordet. = I put/lay the book on the table.
• Jeg legger nøkkelknippet på benken. = I put the keychain on the bench/counter.

Other verbs may be possible in some contexts, but they can sound different:

• sette is often used for placing something upright or setting something somewhere
• putte can mean put in a more casual sense, often into something
• plassere sounds more formal, like place

So legger is a very normal verb here.

på means on, and benken is the definite form of benk.

So:

• en benk = a bench
• benken = the bench

In many everyday contexts, benk can also refer to a counter or worktop, depending on the situation. So på benken means on the bench/counter.

Norwegian uses på for surfaces, just like English uses on:

• på bordet = on the table
• på benken = on the bench/counter

Because in this sentence hjem is not being used like an ordinary noun with an article. It functions more like an adverb of direction.

Compare:

• Jeg drar hjem. = I’m going home.
• Jeg er hjemme. = I’m at home.

You do not say et hjem here, because that would mean a home in a more literal noun sense, not the normal everyday idea of home as destination.

So kommer hjem is just the standard expression for come/get home.

Yes. In standard Norwegian writing, a subordinate clause placed first is followed by a comma.

So:

• Når jeg kommer hjem, legger jeg nøkkelknippet på benken.

That comma helps mark the boundary between the time clause and the main clause.

Yes, very easily. In fact, that is probably the most natural interpretation.

The structure:

• Når ... , ...

often describes what happens regularly:

• Når jeg kommer hjem, legger jeg nøkkelknippet på benken.
• When I get home, I put the keychain on the counter.

This sounds like a routine or habit. If you wanted to make it clearer that it happened only once, the context would usually do that, or you might use past tense in a different sentence.

It breaks down like this:

• Når jeg kommer hjem = subordinate time clause
• legger jeg nøkkelknippet på benken = main clause

More specifically:

• Når = when
• jeg = I
• kommer = come/get
• hjem = home
• legger = put/lay
• jeg = I
• nøkkelknippet = the keychain / bunch of keys
• på benken = on the bench/counter

The key grammar point is that once the sentence opens with the subordinate clause, the main clause uses inversion:

• legger jeg not
• jeg legger