Nej, jeg må aflyse tiden.

Not usually in this sentence. Here må means must, have to, or need to.

So:

• jeg må aflyse tiden = I have to cancel the appointment

Although må is historically related to English may, in modern Danish it often expresses necessity, not permission.

Examples:

• Jeg må gå nu. = I have to go now.
• Du må ikke ryge her. = You must not smoke here.

So in this sentence, må is about obligation or necessity.

Because må is a modal verb, and in Danish modal verbs are followed by the infinitive of the main verb.

Structure:

• jeg = subject
• må = modal verb
• aflyse = main verb in infinitive
• tiden = object

So the pattern is:

subject + modal verb + infinitive + object

Examples:

• Jeg kan komme i morgen. = I can come tomorrow.
• Vi vil købe bilen. = We want to buy the car.
• Hun skal arbejde. = She has to work.

That is why aflyse comes after må.

After a modal verb like må, Danish normally uses the bare infinitive, without at.

So you say:

• jeg må aflyse
• not jeg må at aflyse

This is similar to English:

• I must cancel
• not I must to cancel

Common Danish modal verbs that work this way include:

• kan
• vil
• skal
• må
• bør
• tør

Because tiden is the definite form of tid.

• tid = time / an appointment in some contexts
• tiden = the time / the appointment

In Danish, definiteness is often shown by adding an ending to the noun:

• en tid = a time / an appointment
• tiden = the time / the appointment

In this sentence, tiden refers to a specific scheduled time, so English often translates it as the appointment.

Yes, in the right context it can.

Literally, tid means time, but in everyday Danish it can also mean a scheduled time with someone, such as:

• a doctor’s appointment
• a meeting time
• a booked slot

So aflyse tiden can mean cancel the appointment.

That said, depending on context, Danes might also say:

• aflyse min tid = cancel my appointment
• aflyse aftalen = cancel the appointment/agreement
• aflyse reservationen = cancel the reservation

So tiden is possible, but the exact noun depends on the situation.

Yes, absolutely. Jeg må aflyse min tid is often very natural, especially if you want to make it clear that it is your appointment.

Compare:

• Jeg må aflyse tiden. = I have to cancel the appointment.
• Jeg må aflyse min tid. = I have to cancel my appointment.

Using min can sound more specific and clearer in many real-life situations.

Because Nej functions as a separate response word at the beginning.

So the sentence is divided like this:

• Nej, = No,
• jeg må aflyse tiden. = I have to cancel the appointment.

This is very common in both Danish and English:

• Ja, jeg kommer senere.
• Nej, det kan jeg ikke.

The comma helps mark a short pause after the response word.

Yes, but it means something slightly different.

• Jeg må aflyse tiden. = I have to cancel the appointment
  This emphasizes necessity.
• Jeg aflyser tiden. = I am cancelling the appointment / I cancel the appointment
  This simply states the action.

So if you want to express I need to / I have to, keep må.

Må is usually pronounced roughly like moh, with a rounded vowel.

A few helpful notes:

• å in Danish is a separate letter
• it often sounds somewhat like the vowel in British English more, but shorter and not exactly the same
• må is one syllable

Also:

• jeg is often pronounced more like yai or yei in connected speech, depending on accent
• aflyse is roughly a-fly-se
• tiden is roughly tee-then or tee-dən, depending on pronunciation style

Exact Danish pronunciation can vary, but the key thing is to recognize må as a single-syllable modal verb with å.

Yes, grammatically it is fine. But in real conversation, many speakers might choose a slightly more specific noun depending on the situation.

Very natural alternatives include:

• Nej, jeg må aflyse min tid.
• Nej, jeg må aflyse aftalen.
• Nej, jeg bliver nødt til at aflyse tiden.

The original sentence is understandable and correct, but in everyday Danish the exact wording often depends on what kind of booking or appointment you mean.