Juma alisahau jezi yake ya mpira, kwa hiyo alibaki na sare ya shule.

alisahau can be broken down like this:

• a- = he/she
• -li- = past tense
• -sahau = forget

So alisahau means he/she forgot.

In this sentence, the subject is Juma, so it means Juma forgot.

In Swahili, the subject is usually shown inside the verb itself.

So in alisahau and alibaki:

• a- already means he/she

Because Juma is named explicitly, Swahili does not need an extra separate pronoun like he.

In Swahili, possessives usually come after the noun they describe.

So:

• jezi yake = his jersey
• literally: jersey his

This is normal Swahili word order. English puts the possessive before the noun, but Swahili usually puts it after.

It works like this:

• jezi = jersey
• yake = his
• ya mpira = of football / for football / sports-related

So jezi yake ya mpira means his football jersey.

A very literal breakdown would be:

• jersey his of football

But in natural English, that becomes his football jersey.

That ya is part of agreement with the noun jezi.

jezi belongs to a noun class that often uses ya for connections like:

• possession: jezi yake = his jersey
• description/association: jezi ya mpira = football jersey

So the ya is not exactly the same kind of word each time, but both forms reflect agreement with jezi.

mpira can mean:

• ball
• football
• sometimes more broadly sports/game involving a ball, depending on context

In jezi ya mpira, it usually means something like:

• football jersey
• or sports jersey

If you want to be very specific about football/soccer, Swahili often says mpira wa miguu.

kwa hiyo means:

• so
• therefore
• for that reason

It connects the first idea to the result:

• Juma forgot his football jersey, so he remained with his school uniform

It is a very common way to show consequence.

alibaki na comes from kubaki na, which means:

• to remain with
• to be left with
• to still have

So:

• alibaki na sare ya shule = he was left with his school uniform
• or more naturally, he ended up wearing/with his school uniform

The na is important because kubaki na is the pattern used for remain with something.

It means school uniform.

Breakdown:

• sare = uniform
• ya shule = of school / school

So literally it is uniform of school, which in natural English is school uniform.

Because English often turns noun + of noun expressions into adjective-like phrases.

So:

• sare ya shule
• literally: uniform of school
• naturally: school uniform

This is a very common pattern in Swahili:

• kitabu cha mwanafunzi = student's book
• mlango wa nyumba = house door / door of the house
• sare ya shule = school uniform

Because both verbs have the same subject: Juma.

So:

• alisahau = he forgot
• alibaki = he remained

In both verbs:

• a- = he/she

Swahili repeats the subject marker on each verb, even when the subject has already been mentioned.

Usually, jezi yake ya mpira is the more natural order here.

That order keeps the possessive close to the noun:

• jezi yake = his jersey

Then ya mpira further describes what kind of jersey it is.

So jezi yake ya mpira is the clearest and most natural way to say his football jersey in this sentence.

It mainly means forgot, but in context it can imply forgot and left behind.

So in this sentence, English might understand it as:

• Juma forgot his football jersey
• or Juma left his football jersey behind

The exact wording in English depends on context, but the Swahili verb here is still -sahau = forget.