Så länge du vet vart du ska, behöver du inte skaka på huvudet varje gång någon pekar på kartan.

Så länge means as long as here.

In this sentence, it introduces a condition:

• Så länge du vet vart du ska = As long as you know where you’re going

Be careful, because så länge can also mean for that long / meanwhile / bye for now in other contexts. Here, the grammar makes it clear that it means as long as.

You may also see så länge som, which is a slightly fuller version with the same meaning.

This is about the difference between var and vart:

• var = where (location, no movement)
• vart = where to (direction, movement)

Since du ska suggests movement or destination, Swedish often uses vart:

• vet vart du ska = know where you’re going / where you’re headed

In everyday spoken Swedish, many speakers use var even when standard grammar would prefer vart, so you may hear both. But in careful written Swedish, vart is a good choice here.

Because vart du ska is a subordinate clause, not a main clause.

In Swedish:

• Main clauses usually follow the verb-second rule: Nu ska du gå
• Subordinate clauses do not use that pattern: ... vart du ska

So:

• Vad ska du göra? = main clause question
• Jag vet vad du ska göra. = subordinate clause

Here, vart du ska works like where you’re going, so the word order is normal subordinate-clause order.

Here, ska is not best understood as a simple future marker like English will. In vart du ska, it often means something closer to:

• where you’re going
• where you’re supposed to go
• where you’re headed

Swedish often uses ska in expressions about intended destination or planned movement.

So du vet vart du ska is a very natural way to say you know where you’re going.

This is because of the V2 rule in Swedish main clauses.

The main clause is:

• behöver du inte skaka på huvudet varje gång någon pekar på kartan

Since the sentence begins with a fronted element, namely the subordinate clause

• Så länge du vet vart du ska

the finite verb of the main clause must come next:

• Så länge du vet vart du ska, behöver du inte ...

So the order is:

1. fronted clause
2. finite verb: behöver
3. subject: du
4. sentence adverb: inte

That is standard Swedish word order.

In a main clause, inte usually comes after the finite verb and after the subject.

So:

• du behöver inte skaka ...
• behöver du inte skaka ...

Both follow normal Swedish placement rules for inte.

Compare:

• Jag kommer inte
• Nu kommer jag inte

In subordinate clauses, inte usually comes earlier, before the finite verb:

• ... att du inte vet
• ... eftersom du inte kommer

So the position of inte helps show what kind of clause you are in.

Because after modal-like verbs such as behöva, Swedish normally uses the infinitive without att.

So:

• du behöver inte skaka
• not du behöver inte att skaka

This is similar to English:

• you need not shake
• not you need not to shake

Other common verbs that also often take an infinitive without att include:

• kan
• ska
• vill
• måste
• får

In Swedish, the idiomatic expression for to shake one’s head is skaka på huvudet.

So the på is part of the normal expression.

Compare:

• nicka med huvudet = nod with one’s head
• skaka på huvudet = shake one’s head

Even if English just says shake your head, Swedish usually wants på here.

Swedish often uses the definite form of body parts where English uses a possessive.

So Swedish prefers:

• skaka på huvudet = literally shake on the head

but the meaning is naturally:

• shake your head

This is very common with body parts and clothing, especially when the owner is already obvious from the context.

For example:

• Hon tvättade händerna = She washed her hands
• Han bröt benet = He broke his leg

Varje gång means every time.

So:

• varje gång någon pekar på kartan = every time someone points at the map

It introduces repeated occasions.

Related expressions:

• ibland = sometimes
• ofta = often
• alltid = always
• nästa gång = next time

Because Swedish often uses the present tense in general statements and repeated situations.

Here the sentence describes what happens in a typical situation:

• every time someone points at the map

So the present tense pekar is the natural choice.

It does not have to mean it is happening right now. It can describe a general habit or repeated event.

Någon can often mean either someone or anyone, depending on context.

Here, because it is in a positive clause describing an event, it naturally means:

• someone points at the map

If the sentence were negative or a question, the translation might shift depending on context.

For example:

• Någon kom. = Someone came.
• Kom någon? = Did anyone come?
• Ingen kom. = No one came.

Because when you point at a map, Swedish uses på.

So:

• peka på kartan = point at the map

In Swedish, på is very common for surfaces, targets of pointing, and things you touch or indicate on a surface.

Compare:

• peka på tavlan = point at the board
• peka på bilden = point at the picture

Using i would suggest something more like in the map, which is not what is meant here.

The comma after Så länge du vet vart du ska is acceptable and helpful, because a subordinate clause comes first and is followed by the main clause.

In Swedish, commas are often used a bit less than in English, but this comma is completely natural and makes the sentence easier to read.

So:

• Så länge du vet vart du ska, behöver du inte ...

is good standard punctuation.

Yes. A more neutral word order would be:

• Du behöver inte skaka på huvudet varje gång någon pekar på kartan, så länge du vet vart du ska.

But the original version puts the condition first:

• Så länge du vet vart du ska, ...

That gives it a slightly more logical or emphatic setup: first the condition, then the result.

Both are grammatical, but the original is very natural.

No. Even though the verb comes before the subject, this is not a question.

It looks like question word order because Swedish puts the finite verb before the subject when something else comes first in a main clause.

Compare:

• Du behöver inte skaka på huvudet.
• Så länge du vet vart du ska, behöver du inte skaka på huvudet.

The second one is still a statement, not a question. The first clause has simply taken the first position, so the verb must come next.

The sentence breaks down like this:

• Så länge du vet vart du ska
  = subordinate clause of condition
  = As long as you know where you’re going

• behöver du inte skaka på huvudet
  = main clause
  = you don’t need to shake your head

• varje gång någon pekar på kartan
  = time clause
  = every time someone points at the map

So the full structure is:

condition + main clause + time expression

That is a very common and useful Swedish sentence pattern.