Mwalimu alisema kuwa tusipokuwa na afya nzuri, hatutaweza kuzingatia somo hata kama tutakaa darasani siku nzima.

A useful breakdown is:

• Mwalimu alisema kuwa = the teacher said that...
• tusipokuwa na afya nzuri = if we are not in good health...
• hatutaweza kuzingatia somo = we will not be able to concentrate on the lesson...
• hata kama tutakaa darasani siku nzima = even if we stay in the classroom all day

So the sentence has:

1. a reporting clause
2. an if clause
3. a main result clause
4. an even if clause

Here kuwa works like that in English after said:

• alisema kuwa... = said that...

So it introduces what the teacher said.

Important: this is not the same use as kuwa meaning to be, even though it is the same word form. In this sentence, its job is to connect the reporting verb to the content of the statement.

Also, in everyday Swahili, kuwa is often optional here:

• Mwalimu alisema kuwa...
• Mwalimu alisema...

Both can be natural.

Tusipokuwa means if we are not.

A helpful breakdown is:

• tu- = we
• -sipo- = if not / when not
• -kuwa = be

So:

• tusipokuwa = if we are not

This is a common Swahili negative conditional pattern. Compare:

• ukija = if you come
• usipokuja = if you do not come

So in your sentence:

• tusipokuwa na afya nzuri = if we are not in good health

Swahili often expresses this idea with kuwa na, literally to be with / to have:

• kuwa na afya nzuri = to have good health
• natural English: to be healthy or to be in good health

So the structure is very normal in Swahili. It is not awkward or overly literal for a native speaker.

Because afya takes the adjective form nzuri in this noun class.

So:

• afya nzuri = good health

This is the same adjective form you also see with many other nouns in the same class, such as:

• siku nzuri = a good day
• nyumba nzuri = a good house

So the adjective is agreeing correctly with afya.

Hatutaweza means we will not be able.

It breaks down like this:

• ha- = negation
• tu- = we
• -ta- = future
• -weza = be able

So:

• ha-tu-ta-weza = we will not be able

It is future because this is the result of the condition:

• if we are not healthy, then we will not be able to concentrate

If you used hatuwezi, that would sound more like we cannot / we are not able in a present or general sense.

After kuweza meaning to be able, the next verb normally stays in the infinitive form with ku-:

• kuweza kusoma = to be able to read
• kuweza kuja = to be able to come
• kuweza kuzingatia = to be able to concentrate

So:

• hatutaweza kuzingatia = we will not be able to concentrate

This is very similar to English be able to concentrate.

Because Swahili and English do not always use prepositions in the same places.

In English, you usually say:

• concentrate on the lesson

But in Swahili, kuzingatia can take a direct object:

• kuzingatia somo

So this naturally means:

• concentrate on the lesson
• focus on the lesson

The noun somo here means lesson, though in other contexts it can also mean subject.

Hata kama means even if.

• kama by itself can mean if, and also like/as in other contexts
• hata adds the sense of even

So:

• kama = if
• hata kama = even if

In this sentence, it shows that the result stays true despite that extra condition:

• we will not be able to concentrate, even if we stay in the classroom all day

The verb kaa has a wider meaning than just sit. It can mean:

• sit
• stay
• remain
• live

Here, tutakaa darasani siku nzima is best understood as:

• we will stay in the classroom all day
• we will remain in class all day

It does not have to mean physically sitting every second.

Darasani means in the classroom or in class.

It comes from:

• darasa = class / classroom
• -ni = locative ending, often meaning in / at / to

So:

• darasani = in class / in the classroom

This -ni ending is very common in Swahili:

• nyumbani = at home
• shuleni = at school
• mezani = on the table / at the table

Siku nzima means the whole day or all day.

• siku = day
• nzima = whole, entire

So:

• siku nzima = all day

Swahili often uses time expressions directly, without adding a separate word like English for:

• tutakaa darasani siku nzima = we will stay in the classroom all day

That is completely natural.

Yes. Very often it can be omitted.

So both of these are possible:

• Mwalimu alisema kuwa tusipokuwa na afya nzuri...
• Mwalimu alisema tusipokuwa na afya nzuri...

Using kuwa can make the sentence feel a bit clearer or more explicit, especially in careful or written language, but leaving it out is also common and natural.