Tukishanunua maziwa na mkate, tutakunywa chai nyumbani.

It can be broken into these parts:

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

So tukishanunua means something like when/once we have already bought.

In this sentence, it gives the idea once we’ve bought milk and bread...

-sha- adds the idea of completion: already, by then, or once ... has happened.

So compare:

• tukinunua maziwa na mkate = if/when we buy milk and bread
• tukishanunua maziwa na mkate = once we have bought milk and bread

In this sentence, -sha- helps show that buying happens first, and drinking tea happens after that.

In this sentence, it is more natural to understand it as when/once we have bought.

The -ki- form can sometimes mean if, but with -sha- and the future in the next clause, it often gives a sequence:

• first: we buy
• then: we will drink tea

So the overall feeling is Once we’ve bought milk and bread, we’ll drink tea at home.

In Swahili, subject markers and tense markers are usually attached to the verb.

tutakunywa =

• tu- = we
• -ta- = future
• kunywa = drink

So tutakunywa means we will drink.

This is very normal in Swahili: what English expresses with separate words is often built into one verb form.

Because the action in the main clause happens later than the moment of speaking.

• tukishanunua... = once we’ve bought...
• tutakunywa... = we will drink...

This is a very common pattern in Swahili:

• subordinate clause: when/once X happens
• main clause: future action

So the sentence is structured around a future plan.

Nyumbani means at home / home.

It is a locative form, so Swahili often does not need a separate word like at before it.

So:

• nyumbani = at home
• shuleni = at school
• sokoni = at the market

In this sentence, nyumbani tells the location where the tea-drinking will happen.

Maziwa is the normal Swahili word for milk.

It historically looks like a plural noun form, and grammatically it behaves with plural agreement in many contexts, but in meaning it often refers to milk as a mass noun, not milks.

So a learner should mostly just memorize:

• maziwa = milk

You do not need to force an English singular/plural idea onto it.

Here na means and:

• maziwa na mkate = milk and bread

But na is a very common word in Swahili and can also mean with, depending on context.

For example:

• chai na maziwa = tea with milk
• Juma na Asha = Juma and Asha

So in this sentence, it simply joins the two things being bought.

Swahili does not have articles like a, an, or the.

So:

• maziwa can mean milk, the milk, or some milk
• mkate can mean bread, the bread, or a loaf of bread, depending on context
• chai can mean tea or the tea

The context usually tells you what sounds most natural in English.

Yes, you can, but it changes the nuance.

• tukinunua... = if/when we buy...
• tukishanunua... = once we’ve bought... / after buying...

The version with -sha- is more definite about the first action being completed before the second one happens.

So if you want the sense after we’ve finished buying, tukishanunua is better.

Yes. You could also say:

• Tutakunywa chai nyumbani tukishanunua maziwa na mkate.

That still means roughly We’ll drink tea at home once we’ve bought milk and bread.

Putting the tukishanunua... clause first is very natural because it sets up the condition or time frame before the main action.

Yes. Chai is what we will drink, so it is the object of tutakunywa.

The structure is:

• tutakunywa = we will drink
• chai = tea
• nyumbani = at home

So the second clause is basically:

• we will drink tea at home

Yes. It is a very common and useful pattern:

• tukisha- + verb, tuta- + verb

This often means:

• once we have done X, we will do Y

For example:

• Tukishamaliza kazi, tutarudi nyumbani.
  Once we’ve finished work, we’ll go home.

• Tukishafika, tutakupigia simu.
  Once we arrive, we’ll call you.

So this sentence is a great model for talking about a future sequence of actions.