Korttermynberging is beskikbaar, met dien verstande dat die ontruimingsdatum duidelik is.

Afrikaans usually writes compound nouns as a single word.

• korttermyn = short-term
• berging = storage

So korttermynberging literally combines into short-term-storage.

This is very common in Afrikaans. English often uses spaces or hyphens where Afrikaans prefers one solid compound.

Examples:

• huisdeur = house door / front door
• motorhuis = garage
• werkstyd = working time

Beskikbaar means available. Here it is an adjective used after is.

So the structure is:

• Korttermynberging = subject
• is = verb
• beskikbaar = predicate adjective

This works much like English Storage is available.

Yes, it is a fixed, fairly formal expression.

It means something like:

• provided that
• on the understanding that
• with the proviso that

It is often used in formal notices, contracts, policies, and official writing.

So in this sentence, it introduces a condition: the storage is available, but only under a stated condition.

That is a very good question, because dien is not a common everyday word by itself in modern Afrikaans.

In met dien verstande dat, dien is part of an old fixed expression. You do not usually learn it as a normal standalone word for daily conversation. It survives mainly inside set phrases like this one.

So the safest way to learn it is:

• treat met dien verstande dat as one formal chunk
• do not try to build lots of new sentences with dien on its own

Dat introduces a subordinate clause, just like that in English.

The clause after it is:

• dat die ontruimingsdatum duidelik is

This is the condition being stated.

Afrikaans often uses dat after expressions that introduce explanation, thought, condition, or reported content.

Because after dat, Afrikaans uses subordinate-clause word order, where the finite verb typically goes to the end.

Compare:

• Main clause: Die ontruimingsdatum is duidelik.
• Subordinate clause: dat die ontruimingsdatum duidelik is

This is one of the most important word-order patterns in Afrikaans.

So:

• normal statement: X is duidelik
• after dat: dat X duidelik is

It is another compound noun:

• ontruiming = vacating, clearing out, evacuation, or in some contexts eviction
• datum = date

So ontruimingsdatum means the date on which the place must be vacated or cleared out.

Depending on context, English might render it as:

• move-out date
• vacate date
• eviction date
• clear-out date

In practical property or storage contexts, move-out date or vacate date is often the most natural.

Die is the definite article in Afrikaans, meaning the.

A few useful points:

• Afrikaans uses die for singular and plural definite nouns
• it does not change for gender

So:

• die datum = the date
• die datums = the dates

Here, die ontruimingsdatum refers to the relevant specific vacating date.

Because the sentence is talking about short-term storage in a general sense, not one specific storage unit or a countable item.

This is similar to English:

• Short-term storage is available
  not necessarily
• A short-term storage is available

If you wanted to refer to a specific thing, the wording would probably change.

Yes. Duidelik means clear and is an adjective.

Here it is used predicatively, after is:

• die datum is duidelik

When an adjective comes before a noun in Afrikaans, it often changes form:

• 'n duidelike datum = a clear date

So compare:

• Die datum is duidelik.
• 'n duidelike datum

That contrast is very common in Afrikaans adjectives.

It is fairly formal, mainly because of met dien verstande dat.

A more everyday way to express a similar idea could be:

• Korttermynberging is beskikbaar mits die ontruimingsdatum duidelik is.
• Korttermynberging is beskikbaar solank die ontruimingsdatum duidelik is.

Nuance:

• mits = provided that; still somewhat formal, but simpler
• solank = as long as; more conversational

So the original sentence sounds suitable for official or written communication.

Yes, the comma is natural and expected here.

The phrase met dien verstande dat ... adds a qualification or condition to the main statement, so the comma helps separate:

• the main statement: Korttermynberging is beskikbaar
• the condition: met dien verstande dat ...

In formal written Afrikaans, this punctuation is normal.

Yes. A useful way to break it up is:

• Korttermynberging is beskikbaar
  main statement

• met dien verstande dat die ontruimingsdatum duidelik is
  formal condition attached to the statement

So the overall pattern is:

[Main statement], [formal condition].

That makes it easier to read and reuse in similar sentences.