Tukishanunua vitu vya ofa ya leo, tutarudi nyumbani kabla ya supermarketi kufungwa.

Tukishanunua can be broken down like this:

• tu- = we
• -ki- = if / when
• -sha- = already / once
• -nunua = buy

So tukishanunua means something like:

• if we have already bought
• once we buy
• when we’ve finished buying

In this sentence, it gives the idea once we’ve bought the sale items.

The marker -ki- is often used for a subordinate clause meaning if or when.

So:

• tukinunua = if/when we buy
• tukishanunua = if/when we have already bought / once we buy

In sentences like this one, English often uses when or once, even though Swahili uses the same -ki- form that can also mean if.

The infix -sha- adds the sense of already, by then, or completion before something else happens.

Compare:

• Tukinunua vitu... = When/if we buy the things...
• Tukishanunua vitu... = Once we’ve bought the things...

So -sha- helps show that the buying will be completed first, and then the next action happens: we will return home.

This is because vya must agree with vitu.

• kitu = thing
• vitu = things

Since vitu is a plural noun in the ki-/vi- noun class, the connector meaning of must also match that class:

• singular: cha
• plural: vya

So:

• kitu cha ofa = a sale item
• vitu vya ofa = sale items

That is why the sentence says vitu vya ofa ya leo = today’s sale items.

Here, ya means of and agrees with ofa.

• ofa = offer / sale / promotion
• leo = today

So:

• ofa ya leo = today’s offer / today’s sale

The ya is not agreeing with leo; it is agreeing with ofa.

Tutarudi is the future tense of kurudi (to return).

It breaks down like this:

• tu- = we
• -ta- = future marker
• -rudi = return

So tutarudi means we will return.

This matches the meaning of the sentence, because the returning happens in the future, after the shopping is done.

In Swahili, nyumbani already works as a location word meaning:

• at home
• home
• to home / back home

So you do not need a separate word for to here.

• tutarudi nyumbani = we will return home

This is very natural Swahili.

This part literally means something like:

• before the supermarket being closed

More natural English is:

• before the supermarket closes
• before the supermarket is closed

Here is the structure:

• kabla ya = before
• supermarketi = supermarket
• kufungwa = to be closed / being closed

Swahili often uses kabla ya followed by a noun or verbal noun phrase where English would use a full clause.

So instead of saying a full clause like before the supermarket closes, Swahili can say kabla ya supermarketi kufungwa.

This is because the supermarket is not doing the closing; it is the thing being closed.

• kufunga = to close / to shut
• kufungwa = to be closed

The -w- / -w(a)- element is a passive idea.

So:

• kabla ya kufunga supermarketi would suggest before closing the supermarket
• kabla ya supermarketi kufungwa means before the supermarket is closed

That passive form is the correct one here.

Swahili freely uses many loanwords, especially for modern places and objects. Supermarketi is a borrowed word from supermarket, adapted to Swahili pronunciation and spelling.

This is completely normal. Learners should get used to seeing borrowed words such as:

• benki = bank
• baiskeli = bicycle
• hoteli = hotel
• supermarketi = supermarket

So this word is not strange or incorrect at all.

Yes, depending on context.

Because of -ki- and -sha-, the first clause can be understood as:

• If we’ve bought today’s sale items...
• When we’ve bought today’s sale items...
• Once we’ve bought today’s sale items...

In this sentence, once is probably the most natural English choice, because the speaker sounds confident that the shopping will happen.

So the overall idea is:

• Once we’ve bought today’s sale items, we’ll return home before the supermarket closes.

Yes, it is natural and grammatical.

A learner should especially notice these very common Swahili patterns in it:

• -ki- for if/when
• -sha- for already / once
• noun-class agreement in vya
• future tense in tutarudi
• nyumbani as a location word
• kabla ya + infinitive/passive phrase

So it is a very useful sentence for learning how Swahili links actions in time.