På fredag skal hun til at bestille dessert, og så ringer telefonen.

Most often, på fredag means this coming Friday / next Friday, depending on the point of view in context.

Danish often uses på + weekday for a specific upcoming day:

• på mandag = on Monday / this coming Monday
• på fredag = on Friday / this coming Friday

If you want a repeated meaning, Danish usually uses something else:

• hver fredag = every Friday
• om fredagen = on Fridays

So in this sentence, på fredag is most naturally understood as a specific Friday, not Fridays in general.

This is because Danish main clauses normally follow the V2 rule, which means the finite verb comes in the second position.

Basic order:

• Hun skal til at bestille dessert på fredag

But if you move På fredag to the front, the verb must still stay second:

• På fredag skal hun til at bestille dessert

So the subject hun moves after the finite verb skal.

Not really, or at least not primarily.

Skal can mean must / have to, but it can also express something like will, is going to, or is about to, depending on context.

In this sentence, because of the construction skal til at + infinitive, it means something like:

• is about to
• is just going to start

So here skal is not mainly about obligation. It is part of a phrase describing an action that is just about to begin.

There is an important difference:

• skal bestille dessert = she will order dessert / she has to order dessert
• skal til at bestille dessert = she is about to start ordering dessert

So til at adds the idea of the action beginning.

This is a very common Danish pattern:

• jeg skal til at gå = I am about to leave / I’m going to start leaving
• han skal til at spise = he is about to start eating

It focuses on the moment right before the action starts.

Because Danish can use a noun without an article when speaking about the type of thing involved, especially after certain verbs.

Here:

• bestille dessert = order dessert

This is similar to English, where we can also say order dessert without saying a dessert.

Compare:

• bestille dessert = order dessert, in a general sense
• bestille en dessert = order a dessert, one dessert item
• bestille desserten = order the dessert, a specific dessert already known from the context

So the bare noun sounds natural here.

Og så usually means and then in this kind of sentence.

It is very common in spoken and written Danish when telling a sequence of events:

• first one thing happens
• og så the next thing happens

So here it helps create a narrative flow:

• she is about to order dessert,
• and then the phone rings.

Depending on context, så can sometimes feel a bit like then, so, or next.

Again, this is because of the Danish V2 rule.

In the second clause, så is in the first position of the clause. That means the finite verb must come next:

• så ringer telefonen

The subject telefonen comes after the verb.

So the structure is:

• og = and
• så = first element inside the clause
• ringer = finite verb in second position
• telefonen = subject

If there were no så in front, you could say:

• Telefonen ringer

Because Danish normally uses the definite form when referring to a specific, identifiable thing in the situation.

So:

• telefonen = the phone
• en telefon = a phone
• telefon by itself would not work here as a normal singular count noun

In context, it is the phone present in the situation, so the definite form is natural:

• telefonen ringer = the phone rings

This is very normal Danish usage.

Because Danish often uses the present tense for future situations when the time is already clear from context.

Since på fredag already tells you when it happens, Danish does not need a special future form.

Also, the sentence has a kind of storytelling present feel:

• On Friday she is about to order dessert, and then the phone rings

This makes the event sound vivid and immediate.

So the present tense here is completely natural, even though the time reference is future.

They mean the same basic thing, but the word order depends on what comes first in the clause.

On its own, the normal sentence is:

• Telefonen ringer

But after an element like så, Danish puts the verb second:

• Så ringer telefonen

So the difference is grammatical word order, not a difference in meaning.

Because there are two main clauses:

• På fredag skal hun til at bestille dessert
• så ringer telefonen

In Danish, clauses are usually separated by a comma, including when they are joined by og.

So the comma is there because the sentence contains two coordinated clauses, not because og itself always automatically requires a comma.