Ons besluit of selfberging nodig is al dan nie.

In this sentence, of means whether, not or.

• Ons besluit of selfberging nodig is al dan nie. = We decide whether self-storage is necessary or not.

Afrikaans of can be used to introduce an indirect yes/no question, just like whether in English.

Compare:

• Tee of koffie? = Tea or coffee?
• Ek weet nie of hy kom nie. = I don't know whether he is coming.

So here, of starts the clause whether self-storage is necessary.

Because of introduces a subordinate clause, and in Afrikaans subordinate clauses, the finite verb usually goes to the end.

Main clause word order:

• Selfberging is nodig. = Self-storage is necessary.

Subordinate clause after of:

• ... of selfberging nodig is ...

So the normal is moves to the end of that clause.

This is a very common Afrikaans pattern:

• Ek weet dat hy moeg is.
• Ons vra of dit reg is.

Al dan nie is a set expression meaning or not.

So:

• of selfberging nodig is al dan nie = whether self-storage is necessary or not

You will often see al dan nie after a clause introduced by of when the speaker wants to make the whether or not idea completely explicit.

It is very idiomatic Afrikaans.

Yes. You can say:

• Ons besluit of selfberging nodig is.

This already means We decide whether self-storage is necessary.

Adding al dan nie makes it more explicit:

• ... whether it is necessary or not

So the version with al dan nie is slightly fuller and more emphatic, but both are natural.

Selfberging is a compound noun:

• self = self
• berging = storage / storing / safekeeping

Together, selfberging means self-storage, as in rented storage units or the service of storing your own things.

Afrikaans often forms nouns by combining words into one single compound, so writing selfberging as one word is normal.

Because selfberging is being used in a general sense, like a concept or service.

• Ons besluit of selfberging nodig is ... = We decide whether self-storage is necessary ...

This is similar to English, where you also usually would not say the self-storage in a general statement.

If you were talking about a specific storage arrangement, then Afrikaans could use an article:

• die selfberging = the self-storage / the storage unit / the storage service

But in your sentence, the meaning is general, so no article is needed.

Here, besluit is a verb meaning decide.

• Ons besluit = We decide

Afrikaans verbs often have the same form for different subjects in the present tense:

• ek besluit
• jy besluit
• ons besluit
• hulle besluit

So unlike English, there is no change like decide/decides.

Also, besluit can be a noun in other contexts:

• die besluit = the decision

But in your sentence, it is clearly the verb.

Besluit means decide.
Beslis usually means definitely or certainly, and can also mean settle/determine in some contexts, but it is not the normal everyday choice for decide in this sentence.

So:

• Ons besluit ... = We decide ...

That is the standard and natural wording.

Yes. Nodig means necessary or needed, and here it functions like an adjective/predicative adjective.

• Selfberging is nodig. = Self-storage is necessary.

Afrikaans often uses adjectives after is in this way, just like English:

• Dit is maklik. = It is easy.
• Dit is belangrik. = It is important.
• Dit is nodig. = It is necessary.

The sentence has two parts:

1. Main clause

   • Ons besluit
   • We decide

2. Subordinate clause introduced by of

   • of selfberging nodig is al dan nie
   • whether self-storage is necessary or not

So the full structure is:

• Ons besluit
  • of
    • subordinate clause

This is a very useful pattern in Afrikaans for saying:

• I know whether...
• We ask whether...
• They decide whether...

Yes. In natural English, whether and if can both work in many cases like this.

So these are both good translations:

• We decide whether self-storage is necessary or not.
• We decide if self-storage is necessary or not.

But for understanding the Afrikaans grammar, it is often best to think of of here as whether. That helps distinguish it from English or.