Duppen viser hvor sluken ligger.

In a fishing context:

• duppen = the float / the bobber
• sluken = the lure (especially a metal lure, often a spoon-type lure)

So this sentence is about fishing gear.

A useful detail: sluk can also mean drain in other contexts, but that word is normally et sluk. Here we have sluken with -en, so this is the masculine/feminine/common-gender noun meaning the lure.

Because Norwegian usually puts the definite article at the end of the noun.

• en dupp = a float / a bobber

• duppen = the float / the bobber

• en sluk = a lure
• sluken = the lure

This is one of the most important differences from English. Instead of a separate word like the, Norwegian often adds a suffix to the noun.

viser is the present tense of å vise, which means to show.

So:

• å vise = to show
• viser = shows / is showing

In this sentence, Duppen viser ... means The float shows ...

hvor means where.

In this sentence, it introduces an embedded clause:

• hvor sluken ligger = where the lure is / where the lure lies

So the whole sentence literally means something like:

• The float shows where the lure lies/is located.

This use of hvor is very normal in Norwegian when talking about location.

Because this is an embedded clause, not a direct question.

Compare:

• Hvor ligger sluken? = Where is the lure?
  This is a direct question, so the verb comes before the subject.

• Duppen viser hvor sluken ligger. = The float shows where the lure is.
  This is an embedded clause, so the subject usually comes before the verb.

That word order is very important in Norwegian:

• direct question: Hvor ligger sluken?
• embedded clause: ... hvor sluken ligger

Norwegian often uses verbs like ligge, stå, and sitte where English would simply use be.

Here, ligger is from å ligge, which means to lie or to be lying / to be located.

So:

• sluken ligger literally = the lure lies
• natural English = the lure is / the lure is located

Using ligger sounds natural because the lure is in a physical position somewhere in the water.

If you said hvor sluken er, it might be understandable, but ligger is more idiomatic in this context.

Not always. Norwegian uses ligge more broadly than English uses lie.

It can mean:

• to lie physically
• to be situated
• to be located somewhere

For example:

• Boka ligger på bordet. = The book is lying on the table.
• Byen ligger ved kysten. = The city is on the coast.

So in your sentence, sluken ligger is not strange even if you would not literally say the lure lies in everyday English.

It is a subordinate clause or embedded clause.

The main clause is:

• Duppen viser ... = The float shows ...

The subordinate clause gives the content of what it shows:

• hvor sluken ligger = where the lure is

This is a very common pattern in Norwegian:

• Jeg vet hvor han bor. = I know where he lives.
• Hun ser hva du gjør. = She sees what you are doing.
• Duppen viser hvor sluken ligger. = The float shows where the lure is.

Almost, but the result may sound slightly stiff:

• Duppen = the float
• viser = shows
• hvor = where
• sluken = the lure
• ligger = lies

So a very literal translation is:

• The float shows where the lure lies.

That is correct, but in more natural English many people would say:

• The float shows where the lure is.
• The bobber shows where the lure is.

A rough pronunciation guide is:

• Duppen ≈ DUHP-pen
• viser ≈ VEE-ser
• hvor ≈ voor or vorr depending on accent
• sluken ≈ SLOO-ken
• ligger ≈ LIG-er

A rough full version:

• DUHP-pen VEE-ser voor SLOO-ken LIG-er

A few notes:

• u in duppen is short
• u in sluken is long
• g in ligger is not pronounced like a hard English g at the end; it sounds softer in the overall word
• pronunciation varies by dialect

Yes. A few possible alternatives are:

• Duppen viser hvor sluken er.
  Understandable, but a bit less idiomatic than ligger.

• Duppen viser hvor sluken befinner seg.
  More formal: The float shows where the lure is located.

• Duppen viser hvor sluken ligger i vannet.
  More explicit: The float shows where the lure is in the water.

But your original sentence is short, natural, and idiomatic.

Three big things:

1. Definite nouns take an ending

   • duppen = the float
   • sluken = the lure

2. Embedded clause word order

   • hvor sluken ligger, not hvor ligger sluken

3. Norwegian often uses position/location verbs instead of just be

   • ligger can mean is located / is

If you remember those three points, this sentence becomes much easier to understand.