Ons twyfel of dit moontlik is.

A word-for-word breakdown is:

• Ons = we
• twyfel = doubt
• of = whether / if
• dit = it
• moontlik = possible
• is = is

Very literally, the structure is We doubt whether it possible is, but in natural English that becomes We doubt whether it is possible.

No. Ons can mean:

• we as a subject pronoun: Ons twyfel = We doubt
• our before a noun: ons huis = our house

In your sentence, it clearly means we, because it is followed by the verb twyfel.

Yes, of can mean or, but it also means whether / if in indirect questions or embedded clauses.

Here it means whether:

• Ons twyfel of dit moontlik is = We doubt whether it is possible

So Afrikaans of has two common uses:

• tea of coffee = tea or coffee
• Ek weet nie of hy kom nie = I don’t know whether he is coming

You have to tell from the context which meaning it has.

Afrikaans usually uses:

• of for whether / if in an indirect question
• as for a condition, meaning if in the sense of in the event that

So:

• Ons twyfel of dit moontlik is = We doubt whether it is possible
• As dit reën, bly ons binne = If it rains, we stay inside

In your sentence, this is not a condition. It is a whether clause, so of is the correct word.

Because of introduces a subordinate clause, and in Afrikaans the finite verb often moves to the end of that clause.

Compare:

• Main clause: Dit is moontlik = It is possible
• Subordinate clause: of dit moontlik is = whether it is possible

This is a very common Afrikaans pattern after words like dat, omdat, as, wanneer, and of.

Because moontlik is being used after the verb is, so it is a predicative adjective. In that position, Afrikaans adjectives normally stay in their basic form.

• Dit is moontlik = It is possible

But before a noun, you often use the inflected form:

• 'n moontlike oplossing = a possible solution

So:

• after is -> moontlik
• before a noun -> often moontlike

Usually, no. Afrikaans verbs generally do not change form for different persons in the present tense.

So you get:

• Ek twyfel = I doubt
• Jy twyfel = You doubt
• Ons twyfel = We doubt
• Hulle twyfel = They doubt

That is much simpler than English. The verb twyfel stays the same.

Yes. Dit here works like English it.

• Dit is moontlik = It is possible

Just like in English, the sentence needs that subject pronoun. You would not normally leave it out.

So inside the clause of dit moontlik is, dit is the subject of is.

Not for exactly the same meaning.

• twyfel of ... = doubt whether / if ...
• twyfel daaraan dat ... = doubt that ...

So:

• Ons twyfel of dit moontlik is = We doubt whether it is possible
• Ons twyfel daaraan dat dit moontlik is = We doubt that it is possible

English often uses doubt that, but Afrikaans commonly prefers twyfel of or twyfel daaraan dat, depending on the nuance.

Yes. Ons twyfel of dit moontlik is is a normal and grammatical Afrikaans sentence.

It sounds natural in both speech and writing, and it uses very standard patterns:

• ons as the subject
• twyfel as the verb
• of to introduce a whether clause
• verb-final word order in the subordinate clause

So it is a very useful sentence model to learn.