Om porttelefonen inte fungerar, ringer jag dig när jag står vid ytterdörren.

This is because of the Swedish V2 rule in main clauses: the finite verb usually comes in the second position.

Here, the sentence starts with the whole clause Om porttelefonen inte fungerar. That entire clause counts as the first element. So the main clause has to begin with the verb:

• Om porttelefonen inte fungerar, ringer jag dig ...

If you started directly with the main clause, then you would say:

• Jag ringer dig när jag står vid ytterdörren.

So:

• first position: Om porttelefonen inte fungerar
• second position: ringer
• then subject: jag

Because om porttelefonen inte fungerar is a subordinate clause.

In Swedish, negation like inte usually comes before the finite verb in subordinate clauses.

Compare:

• Porttelefonen fungerar inte.
  main clause

• ... om porttelefonen inte fungerar.
  subordinate clause

This is one of the most important word-order differences in Swedish.

A useful shortcut is:

• main clause: verb before inte
• subordinate clause: inte before verb

Swedish often uses the present tense to talk about the future, especially when the future meaning is already clear from context.

So:

• ringer jag dig = I’ll call you
• när jag står vid ytterdörren = when I’m standing / when I’m at the front door

This is very normal Swedish. You do not need ska here.

You could say:

• ... ska jag ringa dig ...

but that can sound a bit more like an explicit intention or plan. In your sentence, the plain present tense sounds natural and idiomatic.

Because they mean different things:

• om = if
  This introduces a condition.
• när = when
  This introduces a time point or situation.

So the structure is:

• If the intercom doesn’t work,
• I’ll call you when I’m at the front door.

In other words:

1. first there is a condition: Om porttelefonen inte fungerar
2. then there is a time clause: när jag står vid ytterdörren

That -en is the Swedish definite ending, equivalent to English the.

So:

• en porttelefon = an intercom
• porttelefonen = the intercom

and:

• en ytterdörr = a front/outer door
• ytterdörren = the front/outer door

Unlike English, Swedish often puts the at the end of the noun instead of using a separate word.

They are compound nouns, which are very common in Swedish.

• porttelefonen = port

  • telefon
    • -en
      literally something like gate/entrance-phone-the

• ytterdörren = ytter

  • dörr
    • -en
      literally outer-door-the

Swedish makes compounds very freely, often more freely than English. English might use separate words, but Swedish often combines them into one word.

Because dig is the object form of du.

• du = you as the subject
• dig = you as the object

In this sentence, jag is the subject and dig is the person being called:

• Jag ringer dig. = I call you.

Compare:

• Du ringer mig. = You call me.
• Jag ringer dig. = I call you.

Yes, you could say är vid ytterdörren, but står vid ytterdörren is often more natural here.

Swedish frequently uses position verbs like:

• stå = stand
• sitta = sit
• ligga = lie

If someone is physically waiting by a door, står gives a more concrete picture: the person is standing there.

Also:

• vid means by, at, or next to

So:

• står vid ytterdörren = am standing by / at the front door

Är vid ytterdörren is more neutral and less visual.

Not always.

In modern Swedish, a comma after an introductory subordinate clause is often optional, especially in a short, clear sentence.

So both of these are possible:

• Om porttelefonen inte fungerar, ringer jag dig när jag står vid ytterdörren.
• Om porttelefonen inte fungerar ringer jag dig när jag står vid ytterdörren.

The comma can help readability, but many writers would leave it out.

Yes. Funkar is a common, more informal alternative to fungerar.

So you might hear:

• Om porttelefonen inte funkar, ringer jag dig ...

That sounds natural in speech and casual writing.

The difference is mainly register:

• fungerar = more neutral/standard
• funkar = more informal/everyday

Both are very common.