Hvis der ikke er mere müsli i skabet, laver min kone varme havregryn til hele familien.

Because Danish usually follows the verb-second (V2) rule in main clauses.

The Hvis clause comes first:

Hvis der ikke er mere müsli i skabet, ...

Once that whole clause takes the first position, the finite verb of the main clause must come next:

... laver min kone varme havregryn ...

So the structure is:

• first position: Hvis der ikke er mere müsli i skabet
• second position: laver
• then the subject: min kone

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

Min kone laver varme havregryn til hele familien.

Here der er is the Danish way to say there is / there are in an existential sense.

So:

• Der er müsli i skabet = There is muesli in the cupboard
• Der er ikke mere müsli i skabet = There isn’t any more muesli in the cupboard

This der does not mean there in the location sense. It is a grammatical placeholder, like English there in there is.

Because this is a subordinate clause introduced by Hvis.

In Danish, sentence adverbs like ikke are usually placed:

• after the finite verb in a main clause
• before the finite verb in a subordinate clause

Compare:

• main clause: Der er ikke mere müsli
• subordinate clause: Hvis der ikke er mere müsli

So ikke moves in front of er because of the subordinate clause.

Yes, literally mere means more, but after a negative it often means any more / any left.

So:

der ikke er mere müsli
means something like:

• there isn’t any more muesli
• there’s no muesli left

This is very common with uncountable or mass nouns:

• Der er ikke mere mælk = There isn’t any more milk
• Jeg har ikke mere kaffe = I don’t have any more coffee

Because skabet is the definite form: the cupboard / the cabinet.

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

• et skab = a cupboard
• skabet = the cupboard

So i skabet means in the cupboard, referring to a specific cupboard already understood from the situation.

Because i means in, and a cupboard is treated as an enclosed space here.

So:

• i skabet = in the cupboard

If something were physically on top of the cupboard, you would use på:

• på skabet = on the cupboard

Because lave is the normal verb for making / preparing food.

So:

• lave mad = make food / cook
• lave havregryn = make oatmeal / prepare oats

gøre is used in many other cases, but not usually for preparing a dish. For food, lave is the natural choice.

Because havregryn is treated as a plural-form noun here, so the adjective takes the plural -e form:

• varm = common singular
• varmt = neuter singular
• varme = plural / definite form

So:

varme havregryn = warm oats / hot oatmeal

Even though English might use singular oatmeal, Danish uses havregryn, which has a plural-looking form and commonly takes varme.

Because havregryn is being used as a mass/substance noun here, not as a single countable item.

So Danish does not need an article in this kind of phrase:

• laver varme havregryn = makes hot oatmeal
• spiser brød = eats bread
• drikker kaffe = drinks coffee

If you were talking about one specific oat flake, that would be different, but that is not what is happening here.

Til often means for / for the benefit of / intended for when talking about giving, preparing, or making something for someone.

So:

laver varme havregryn til hele familien
= makes hot oatmeal for the whole family

Using til here sounds natural because the oatmeal is being prepared for them as the intended recipients.

English often uses just for, but Danish often prefers til in this kind of context.

It means the whole family or the entire family.

• hele = whole / entire
• familien = the family

So til hele familien means the oatmeal is for everyone in the family, not just one person.

Yes, but Danish often uses the present tense for general conditions, repeated actions, or predictable future results.

So this sentence has the sense of:

• If there isn’t any more muesli in the cupboard, my wife makes hot oatmeal for the whole family
• or more naturally in English, If there’s no more muesli, my wife will make hot oatmeal...

Danish does not need a separate future form here. Present tense is normal.

Yes, müsli is commonly used in Danish as a loanword.

The spelling with ü is very common, especially on packaging and in writing, although Danish is generally flexible with some loanwords. In everyday Danish, people still pronounce and use it as an ordinary noun.

So in this sentence, müsli is perfectly normal Danish usage.