Ten spyte daarvan dat die wagtydperk lank is, begin die bloedskenking.

It is a fixed expression meaning despite the fact that or in spite of the fact that.

It is built in parts:

• ten spyte van = in spite of
• daarvan = of that
• dat = that

So:

• Ten spyte daarvan dat die wagtydperk lank is
  = Despite the fact that the waiting period is long

Afrikaans often uses this longer structure before a whole clause. If you only want to refer to a noun phrase, you can use a shorter version:

• Ten spyte van die lang wagtydperk = In spite of the long waiting period

So the longer version is used because what follows is a full clause: die wagtydperk lank is.

Dat introduces a subordinate clause, like English that.

In this sentence:

• Ten spyte daarvan dat ...

the word dat signals that the next part is a dependent clause:

• die wagtydperk lank is

This is very common in Afrikaans after expressions like:

• ek dink dat ... = I think that ...
• omdat ... = because ...
• ten spyte daarvan dat ... = despite the fact that ...

So dat is there because the phrase needs a full clause after it, not just a noun.

Because that part is a subordinate clause, and in Afrikaans subordinate clauses usually send the finite verb to the end.

Compare:

• Main clause: Die wagtydperk is lank.
• Subordinate clause: ... dat die wagtydperk lank is

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

So:

• die wagtydperk is lank = normal statement
• dat die wagtydperk lank is = subordinate-clause order

This happens because the sentence starts with another element: the subordinate clause.

Afrikaans follows a verb-second pattern in main clauses. That means the finite verb usually comes second in the sentence, even if something other than the subject comes first.

Here, the first element is:

• Ten spyte daarvan dat die wagtydperk lank is

So the verb of the main clause must come next:

• begin

Then comes the subject:

• die bloedskenking

So:

• Die bloedskenking begin. = neutral word order
• Ten spyte daarvan dat ..., begin die bloedskenking. = inversion after fronting

This is very normal Afrikaans word order.

Daarvan literally means of that.

In this expression, it helps link ten spyte van to the clause introduced by dat. You can think of:

• ten spyte van = in spite of
• daarvan dat ... = of the fact that ...

Together:

• ten spyte daarvan dat ... = in spite of the fact that ...

It may feel a bit roundabout to an English speaker, but it is a standard Afrikaans pattern.

This is a very common learner question.

Afrikaans usually uses:

• lang before a noun
• lank after a verb like is

Compare:

• 'n lang wagtydperk = a long waiting period
• Die wagtydperk is lank. = The waiting period is long.

So in your sentence, lank is correct because it comes after is and describes the waiting period predicatively.

Wagtydperk means waiting period.

It is a compound noun:

• wag = wait
• tydperk = period

Afrikaans, like Dutch and German, very often writes compound nouns as one word. English sometimes does this too, but less consistently.

Other examples:

• huisdeur = house door / front door
• skooltas = school bag
• bloedskenking = blood donation

So wagtydperk being one word is completely normal Afrikaans spelling.

Bloedskenking means blood donation.

It is another compound noun:

• bloed = blood
• skenking = donation / gift

Afrikaans normally joins these into one word:

• bloedskenking

This is very typical of the language. English often keeps similar expressions as two words, but Afrikaans usually combines them.

Yes, the comma is standard here.

The sentence begins with a subordinate clause:

• Ten spyte daarvan dat die wagtydperk lank is

and then moves to the main clause:

• begin die bloedskenking

Afrikaans normally uses a comma to separate a fronted subordinate clause from the main clause. So the punctuation here is natural and helpful.

Yes.

You could say:

• Die bloedskenking begin ten spyte daarvan dat die wagtydperk lank is.

That is also grammatical.

The version with the subordinate clause first:

• Ten spyte daarvan dat die wagtydperk lank is, begin die bloedskenking.

puts more emphasis on the contrast or concession: despite that fact, the donation begins.

So the choice is partly about style and emphasis, not just grammar.