Når jeg kommer til holdeplassen, ser det ut til at bussen allerede står der.

In Norwegian, the present tense is very often used for future meaning, especially after time words like når (when).

So:

• Når jeg kommer til holdeplassen ... = When I get to the bus stop ...

This is very similar to English, which also often uses the present after when:

• When I arrive, ...
• not usually When I will arrive, ...

So the Norwegian present tense here is completely normal.

Når is used for:

• something in the future
• something repeated or habitual
• general when

Da is usually used for:

• one specific event in the past

So here, because the sentence is about a future situation, når is the right choice.

• Når jeg kommer til holdeplassen ... = When I get to the bus stop ...
• Da jeg kom til holdeplassen ... = When I got to the bus stop ...

This is because of Norwegian V2 word order in main clauses.

The first part of the sentence, Når jeg kommer til holdeplassen, takes the first position. After that, the finite verb of the main clause must come second. That is why you get:

• Når jeg kommer til holdeplassen, ser det ut til at ...

not:

• Når jeg kommer til holdeplassen, det ser ut til at ...

So the order is:

1. fronted element: Når jeg kommer til holdeplassen
2. finite verb: ser
3. subject: det

This is a very common Norwegian pattern.

Ser det ut til at ... means it looks like ... or it seems that ...

It is a very common expression in Norwegian.

Literally, it is something like:

• looks it out to that ...

But you should learn it as a fixed expression:

• Det ser ut til at bussen allerede står der.
• It looks like the bus is already there.

The det here is a dummy subject, similar to it in English it seems.

Because ser ut til at is the normal full structure of the expression when it is followed by a whole clause.

• Det ser ut til at bussen står der.
• It looks like the bus is there.

You can think of it as one unit:

• se ut til at = seem/look as if

If what follows is a noun phrase instead of a clause, Norwegian may use slightly different phrasing, but in your sentence til at is the natural form.

Holdeplassen means the stop, here specifically the bus stop or the stop being talked about.

It comes from:

• holdeplass = stop
• holdeplassen = the stop

Norwegian usually adds the definite article to the end of the noun instead of using a separate word like the.

So:

• en holdeplass = a stop
• holdeplassen = the stop

Because komme til means come/get to or arrive at a place.

So:

• komme til holdeplassen = get to the bus stop

But if you want to say that someone is already at the stop, then på holdeplassen is natural:

• Jeg er på holdeplassen. = I am at the bus stop.

So the difference is roughly:

• til = movement toward / arrival
• på = location at the place

Because it refers to a specific bus that is already understood from the situation.

• buss = bus
• en buss = a bus
• bussen = the bus

In context, it means the bus the speaker is expecting or talking about, so Norwegian uses the definite form.

Because the clause at bussen allerede står der is a subordinate clause introduced by at.

In subordinate clauses, words like ikke and many adverbs are often placed before the finite verb. So this order is natural:

• at bussen allerede står der

A learner often notices that Norwegian word order changes depending on whether the clause is a main clause or a subordinate clause. That is what is happening here.

Norwegian often uses position verbs much more than English does.

So for something stationary, Norwegian may say:

• står = stands / is standing

Even for vehicles, this is very common when they are stopped or waiting.

So:

• bussen står der = the bus is there / the bus is standing there

In natural English, you would usually just say the bus is there, but Norwegian often prefers står in this kind of situation.

Der means there.

Here it refers to the place already being discussed: the bus stop.

So:

• bussen allerede står der
• the bus is already there

It avoids repeating på holdeplassen. Norwegian does this very naturally.

Yes, that is possible, and it can sound a little more explicit.

• komme til holdeplassen = get to the bus stop
• komme fram til holdeplassen = arrive/reach the bus stop

Fram adds the idea of actually reaching the destination. In many contexts, both are natural, though kommer til holdeplassen is already perfectly fine.