Wij kunnen nog niet zekeren, laat staan topropen.

It means not yet, not just not.

So Wij kunnen nog niet zekeren suggests that the situation may change later: right now they do not have that ability, but they may learn it.

• niet = not
• nog niet = not yet

That is a very common Dutch combination.

That is normal Dutch word order.

In a main clause, the finite verb usually comes in second position. Here, kunnen is the finite verb, so it comes right after Wij:

• Wij kunnen ...

The other verb, zekeren, is an infinitive and goes toward the end of the clause:

• Wij kunnen nog niet zekeren.

This is very typical after modal verbs like:

• kunnen = can
• moeten = must
• willen = want
• mogen = may
• zullen = will / shall

Because after kunnen, Dutch uses a bare infinitive.

So you say:

• kunnen zekeren
• kunnen topropen

not:

• kunnen te zekeren
• kunnen te topropen

This is the same pattern used with other modal verbs too.

Laat staan is a fixed expression meaning let alone or much less.

It introduces something that is even less possible, less likely, or more difficult than the thing mentioned before it.

So the logic is:

• we cannot even do A
• let alone do B, which is an even bigger step

In this sentence:

• nog niet zekeren is the first step
• topropen is presented as an even further step

Also, laat staan is idiomatic here. You should not try to understand it literally from laten and staan.

Because Dutch often leaves out repeated words when they are already clear from the context.

The full idea is:

• Wij kunnen nog niet zekeren, laat staan [kunnen] topropen.

The second kunnen is understood, so it is omitted.

English does the same thing:

• We can’t belay yet, let alone top-rope.

You do not need to repeat can in English either.

Yes, in this sentence it is clearly climbing terminology.

In general Dutch, zekeren can have broader meanings related to securing, making safe, or ensuring. But in climbing, zekeren specifically means to belay.

So the exact meaning depends on context. In a climbing context, Dutch speakers will naturally understand it as belaying.

Yes. It is climbing jargon, based on the English term top-rope, but used as a Dutch verb.

This kind of borrowing is common in sports and technical language. So within climbing circles, topropen is quite natural.

Outside that context, some speakers might prefer a more explanatory phrase, but climbers will usually understand topropen immediately.

Yes. Both mean we.

• we = the more common unstressed form in everyday speech
• wij = the full form, often slightly more emphatic, careful, or formal

So both of these are possible:

• Wij kunnen nog niet zekeren, laat staan topropen.
• We kunnen nog niet zekeren, laat staan topropen.

In ordinary spoken Dutch, we would probably be more common.

Because laat staan introduces a separate contrasting add-on: let alone ...

The comma helps mark that break in the sentence. In practice, Dutch often writes this expression with a comma before it:

• Wij kunnen nog niet zekeren, laat staan topropen.

So the punctuation matches the meaning and rhythm of the sentence.