Papai likiiva, tutalikata baada ya chakula cha mchana.

Because Swahili uses noun-class agreement.
The noun papai belongs to the class that often takes li- for singular agreement.

So once papai has been mentioned, other words that refer back to it often show that class agreement:

• li-ki-iva = when/if it ripens
• tu-ta-li-kata = we will cut it

That li- is basically pointing back to papai as it.

likiiva can be broken down like this:

• li- = subject marker agreeing with papai
• -ki- = if/when
• -iva = verb stem from kuiva = to ripen / become ripe

So:

li-ki-iva = if/when it ripens or when it is ripe

In natural English, this is often best translated with when rather than a very literal if.

It can mean either, depending on context.

In Swahili, -ki- often introduces a condition or time relationship:

• if
• when
• whenever

In this sentence, because ripening is expected rather than doubtful, English usually prefers when:

• Papai likiiva... = When the papaya ripens / When the papaya is ripe...

So the form is conditional in structure, but the meaning here is very naturally when.

tutalikata breaks down as:

• tu- = we
• -ta- = future marker
• -li- = object marker for it referring to papai
• -kata = cut

So:

tu-ta-li-kata = we will cut it

This is a very common Swahili pattern:
subject + tense + object + verb stem

Because in Swahili, object pronouns are often attached directly to the verb.

So instead of saying something like we will cut it with a separate word for it, Swahili puts it inside the verb:

• tutalikata = we-will-it-cut

That -li- inside the verb is doing the job of it.

Literally, it is something like:

• baada ya = after
• chakula = food / meal
• cha mchana = of midday / of the daytime

So chakula cha mchana is the usual way to say lunch or midday meal.

Then:

baada ya chakula cha mchana = after lunch

A very literal translation would be after the meal of midday.

Because the connector must agree with chakula, not with mchana.

This is another noun-class agreement point:

• chakula belongs to the ki-/vi- class
• the associative connector for that class is cha

So:

• chakula cha mchana = meal of midday / lunch

If the head noun belonged to a different class, the connector would change.

Because the two clauses do different jobs.

• likiiva gives the condition/time: when it ripens
• tutalikata gives the main future action: we will cut it

In Swahili, the -ki- form already carries the idea of when/if, so you do not normally add a future marker there.

So the pattern is:

• When X happens, we will do Y

That is why only the main verb has -ta-.

It can suggest either, depending on how you want to express it in English.

The verb kuiva means to ripen, to become ripe, or to be ripe depending on context.
So papai likiiva can be understood as:

• when the papaya ripens
• when the papaya is ripe

In normal English, when the papaya is ripe often sounds the most natural if you are talking about the right time to cut it.

Yes, grammatically that is possible:

• If the papaya ripens, we will cut it after lunch.

But in context, when is usually better, because the ripening is being treated as something expected, not doubtful.

So both are possible, but when is the more natural choice here.

Yes, the agreement would change in the plural.

A common plural is mapapai.
Then the agreement would follow that plural noun class instead of singular li-.

For example, the sentence would change along the lines of:

• Mapapai yakiiva, tutayakata baada ya chakula cha mchana.

Here the agreements change because mapapai is plural:

• ya-ki-iva = when they ripen
• tu-ta-ya-kata = we will cut them

So the core meaning stays the same, but the agreement markers change.

Yes. It is very natural.

The structure is:

• Papai likiiva = conditional/time clause first
• tutalikata = main clause
• baada ya chakula cha mchana = time expression at the end

So the sentence is organized as:

When the papaya is ripe, we will cut it after lunch.

That order is completely normal in Swahili, just as it is in English.