Øvingsfilen er nyttig hjemme så vel som på korøvelsen.

Because Norwegian usually writes compound nouns as one word.

• øvingsfilen = øvings
  • fil
    • -en
• korøvelsen = kor
  • øvelse
    • -n/-en

This is more compact than English, where similar expressions are often written as two words, such as practice file or choir rehearsal. In Norwegian, splitting these up would usually look wrong.

That -s- is a linking sound/letter often used in Norwegian compounds. It does not mean possession here.

So øvingsfil is not the file of the exercise in a grammatical possession sense. It is simply the normal compound form meaning something like practice file or rehearsal file.

Norwegian compounds sometimes use a linking -s-, sometimes not. You often just have to learn which form is standard.

The ending -en marks the definite singular form, roughly like the in English.

• en fil → filen = the file
• en øvelse → øvelsen = the rehearsal/exercise

In compounds, the definite ending goes on the last part:

• øvingsfil → øvingsfilen
• korøvelse → korøvelsen

So the whole compound becomes definite by adding the ending at the end.

After er, Norwegian uses a predicative adjective, and it agrees with the subject in number.

Here the subject is singular, so nyttig is correct:

• Øvingsfilen er nyttig.

If the subject were plural, you would normally use nyttige:

• Øvingsfilene er nyttige.

In this sentence, the singular form is the natural one.

Because hjemme is already an adverb meaning at home.

So Norwegian says:

• Jeg er hjemme = I am at home

You do not need a separate word for at here.

It also helps to compare:

• hjemme = at home (location)
• hjem = home in the sense of direction, as in go home

For example:

• Jeg er hjemme = I am at home
• Jeg går hjem = I am going home

Så vel som means as well as. In this sentence, it links the two places where the file is useful:

• hjemme
• på korøvelsen

So it gives the idea of useful at home as well as at choir rehearsal.

It is a perfectly correct expression, but it can sound a little more formal or written than some alternatives.

Yes, absolutely. That is a very natural alternative.

• Øvingsfilen er nyttig både hjemme og på korøvelsen.

This often sounds a bit more everyday and conversational than så vel som.

Very roughly:

• så vel som = as well as
• både ... og ... = both ... and ...

In this sentence, both versions work well.

In Norwegian, på is very common with events, activities, and organized settings.

So you often hear:

• på skolen = at school
• på jobb = at work
• på trening = at practice/training
• på møte = at a meeting
• på øvelse = at rehearsal

That is why på korøvelsen is natural: it means at the choir rehearsal.

If you used i, it would sound more like inside or within the rehearsal, which is not the normal choice here.

The definite form suggests a specific or contextually known rehearsal.

So på korøvelsen can mean something like:

• at the choir rehearsal
• at our choir rehearsal
• at the rehearsal we are talking about

That is very natural when speaker and listener already know which choir activity is meant.

A more general indefinite version, på korøvelse, is possible in some contexts, but på korøvelsen sounds more anchored in a real, known situation.