Siste forbruksdag nærmer seg. I så fall starter matserveringen.

It is a food-label term meaning the product should be eaten by that date. In natural English, it is usually closest to use-by date.

Literally:

• siste = last
• forbruksdag = consumption day / day for use

So the literal wording is something like last day for consumption, but English normally uses use-by date, not a word-for-word translation.

It is also different from best før, which is more like best before.

Because siste is the form used before a noun.

Compare:

• siste dag = the last day
• siste forbruksdag = the last use-by day

But sist is often used as an adverb or after the verb:

• Han kom sist = He came last
• Jeg så henne sist i går = I saw her last yesterday

So before forbruksdag, Norwegian uses siste.

That is because this kind of wording can be very compact, especially in notices, warnings, labels, or app-style messages.

A fuller, more explicitly marked version would often be:

• Den siste forbruksdagen nærmer seg.

The version without den feels shorter and more label-like. Since siste forbruksdag is also a fixed term on food packaging, it is natural to see it written this way in short informational text.

It is a compound noun:

• forbruk = consumption, use
• dag = day

So forbruksdag is literally consumption day.

This is very typical in Norwegian: nouns are often joined into one word. English usually writes similar expressions as separate words, but Norwegian prefers compounds.

Because the verb is å nærme seg, which means to approach or to draw near.

The seg is part of the verb here. It is a reflexive construction, and in English we usually do not translate it word for word.

So:

• Siste forbruksdag nærmer seg = The use-by date is approaching

You will see the same pattern in many common sentences:

• Julen nærmer seg = Christmas is approaching
• Eksamen nærmer seg = The exam is approaching

It means if so or in that case.

Literally, it is something like in such case, but English normally uses:

• if so
• in that case

So the second sentence is introducing what happens under that condition.

Because Norwegian follows the verb-second rule in main clauses.

When something other than the subject comes first, the finite verb still has to stay in second position.

So:

• Matserveringen starter i så fall = neutral order
• I så fall starter matserveringen = adverbial moved to the front

In the second version:

1. I så fall comes first
2. starter must come second
3. matserveringen comes after the verb

This is a very important Norwegian word-order pattern.

It means the food service, the serving of food, or the meal service, depending on context.

It is a compound:

• mat = food
• servering = serving / service
• -en = the definite ending

So:

• matservering = food service / serving of food
• matserveringen = the food service

Norwegian usually writes compound nouns as one word, unlike English.

Because it is definite: the food service, not just food service in general.

Compare:

• matservering = food service, food serving
• matserveringen = the food service

Norwegian often adds definiteness at the end of the noun instead of using a separate word like the.

So -en here is doing the job that the would do in English.

Yes, often you could.

Both starter and begynner can mean starts / begins.

Very roughly:

• starte often sounds a bit more like starting an operation, service, program, or process
• begynne is a more general begin

So matserveringen starter is completely natural, especially if the idea is that a service or scheduled activity begins.

Yes. In standard modern Norwegian, i så fall is written as three separate words.

You may sometimes see isåfall, especially in informal writing, but i så fall is the standard form learners should use.