Sy knap die versamelstuk op, tensy dit te beskadig is.

Because opknap is a separable verb in Afrikaans. Its basic dictionary form is opknap, meaning something like to fix up, to spruce up, or to restore.

In a main clause, the verb splits:

• Sy knap die versamelstuk op.

But in forms where the verb stays together, you may see:

• om die versamelstuk op te knap
• Hy wil dit opknap

This is similar to separable verbs in Dutch and somewhat like phrasal verbs in English, though the grammar is more regular in Afrikaans.

Here opknap means to repair or improve the condition of something, often something old, worn, or in need of attention.

Depending on context, it could be:

• fix up
• restore
• refurbish
• spruce up

Because the object is die versamelstuk, the idea is probably not just ordinary repair, but careful improvement or restoration of a collectible item.

Versamelstuk is a compound noun:

• versamel = collect
• stuk = piece / item

So versamelstuk literally means collection piece, and in natural English it usually corresponds to:

• collectible
• collector’s item

Afrikaans often forms nouns this way by combining smaller words into one compound.

Tensy means unless.

It introduces an exception:

• Sy knap die versamelstuk op, tensy dit te beskadig is. = She fixes up the collectible, unless it is too damaged.

So the main action happens, but only if the condition after tensy does not block it.

Because tensy introduces a subordinate clause, and in Afrikaans subordinate clauses typically send the finite verb to the end.

So:

• main clause: Sy knap die versamelstuk op
• subordinate clause: tensy dit te beskadig is

This is a very common Afrikaans pattern:

• omdat dit duur is
• as hy kom
• terwyl sy werk

English does not usually do this, so it is something English speakers often need to get used to.

Yes. In this sentence, te means too.

So:

• beskadig = damaged
• te beskadig = too damaged

This is a common Afrikaans pattern:

• te groot = too big
• te duur = too expensive
• te laat = too late

So dit te beskadig is means it is too damaged.

Because dit is the normal pronoun for it, especially for things and objects.

Since die versamelstuk is an object, Afrikaans refers back to it with dit:

• die versamelstuk → dit

Afrikaans does not assign grammatical gender to nouns the way some other languages do, so using dit here is straightforward.

Here beskadig is functioning as an adjective.

In:

• dit is te beskadig

the meaning is it is too damaged, where damaged describes the condition of the item.

But beskadig can also appear in verbal contexts related to damage. In this sentence, though, it is clearly describing the state of the object.

Yes, a closely related alternative would be:

• Sy knap die versamelstuk op as dit nie te beskadig is nie.

That means:

• She fixes up the collectible if it is not too damaged.

This is very close in meaning to the original sentence with tensy, but the structure is different:

• tensy = unless
• as ... nie ... nie = if ... not

Both are natural, but tensy is a compact way to express the exception.

The comma separates the main clause from the subordinate clause.

Main clause:

• Sy knap die versamelstuk op

Subordinate clause:

• tensy dit te beskadig is

In Afrikaans, it is normal to use a comma before a clause introduced by words like tensy, especially when it follows the main clause. This helps make the sentence structure clear.