Kompassen hjälpte när jag var vilse.

Kompassen is the definite singular form, meaning the compass.

• en kompass = a compass
• kompassen = the compass

Swedish usually adds the definite ending to the noun itself, instead of using a separate word like the.

Hjälpte is the past tense of hjälpa (to help).

• hjälpa = to help
• hjälper = helps / is helping
• hjälpte = helped
• hjälpt = helped (supine / past participle in some uses)

So Kompassen hjälpte means The compass helped.

In Swedish, you can say hjälpa without stating the object if it is already understood from context.

So Kompassen hjälpte när jag var vilse literally looks like:

• The compass helped when I was lost

In natural English, we often say The compass helped me when I was lost, but Swedish does not need to include mig here unless you want to emphasize it:

• Kompassen hjälpte mig när jag var vilse = The compass helped me when I was lost

Both are possible, but leaving out mig is very natural.

Here när means when.

It introduces a time clause:

• när jag var vilse = when I was lost

This is a very common subordinating conjunction in Swedish.

Because this is a subordinate clause, not a question.

In a normal subordinate clause introduced by när, Swedish keeps the usual subject-verb order:

• när jag var vilse = when I was lost

If you said när var jag vilse, that would sound like a direct question:

• När var jag vilse? = When was I lost?

So the sentence uses normal clause order because it is stating information, not asking a question.

Var is the past tense of är (is/am/are), from the verb vara (to be).

• jag är vilse = I am lost
• jag var vilse = I was lost

So var means was here.

Vilse means lost, especially in the sense of not knowing where you are or not knowing the way.

For example:

• Jag är vilse. = I am lost.
• Barnet kom vilse i skogen. = The child got lost in the forest.

It is the natural word to use when talking about being unable to find your way.

Vilse is one of those Swedish words that usually stays the same in this kind of expression.

In jag var vilse, it works as a predicate expression after vara:

• Jag är vilse
• Han är vilse
• De är vilse

It does not change like many regular adjectives do. So you do not need to worry about adding endings here.

Sometimes, but vilse is much more natural here.

• vilse = lost in the sense of direction, unable to find your way
• förlorad = lost, but often more like gone, missing, lost emotionally, or lost in a broader sense

So for a sentence about a compass, vilse is the best fit, because a compass helps when you do not know where you are.

It can be understood either way depending on context.

Most directly, it sounds like a past situation:

• The compass helped when I was lost.

But Swedish simple past can also be used in storytelling or to describe a completed situation without specifying exactly when.

If you wanted to make it clearly habitual, you would usually add more context, for example:

• Kompassen hjälpte alltid när jag var vilse. = The compass always helped when I was lost.

If you want to make the person helped more explicit, you can say:

• Kompassen hjälpte mig när jag var vilse.

If you want to emphasize I, Swedish can also use stress in speech, and sometimes wording changes depending on context. But the most common way to make the object explicit is simply to add mig.

Yes, it is natural and correct.

It is a simple, clear sentence with:

• a definite noun: Kompassen
• a past tense verb: hjälpte
• a time clause: när jag var vilse

A very close literal structure is:

• The compass helped when I was lost

And that is fully idiomatic in Swedish.