Kemeja putih saya terkena saus pedas saat makan malam.

In Indonesian, the usual order is:

noun + adjective + possessor

So:

kemeja = shirt
putih = white
saya = my

That gives kemeja putih saya = my white shirt.

This is different from English, where possessors usually come first. Indonesian often puts saya, Anda, dia, etc. after the noun phrase when they mean my, your, his/her, and so on.

Here, saya means my.

By itself, saya usually means I, but when it comes after a noun, it works as a possessive:

kemeja saya = my shirt
rumah saya = my house

So in kemeja putih saya, saya is not the subject. It is showing ownership.

Terkena means something like got hit by, got affected by, or got on it.

In this sentence, kemeja putih saya terkena saus pedas means the shirt was affected by the spicy sauce — for example, sauce got spilled, splashed, or smeared onto it.

It often suggests something happened to the subject, often unintentionally or undesirably.

Other examples:

terkena hujan = got caught in the rain
terkena debu = got covered with dust / got dust on it
terkena masalah = got into trouble / was affected by a problem

Both can be used, but they feel a little different.

kena is very common in everyday speech and is more informal.
terkena is more neutral or slightly more formal/written.

So:

Kemeja putih saya kena saus pedas
and
Kemeja putih saya terkena saus pedas

both sound natural, but terkena is a bit neater or more standard in writing.

Literally, it means spicy sauce:

saus = sauce
pedas = spicy

Depending on context, English might translate it as hot sauce, but grammatically it is simply sauce + spicy, because Indonesian usually puts adjectives after nouns.

So:

saus pedas = spicy sauce
baju merah = red shirt
rumah besar = big house

Because that is the normal pattern in Indonesian:

noun + adjective

Examples:

kemeja putih = white shirt
mobil baru = new car
makanan enak = delicious food

This is one of the first word-order differences English speakers usually notice, since English normally uses adjective + noun.

Saat means when or during.
Makan malam can mean to eat dinner or dinner depending on context.

So saat makan malam means:

while eating dinner
or
during dinner

In this sentence, both ideas work well in English.

Indonesian often leaves out subjects when they are obvious from context.

So saat makan malam does not explicitly say when I was eating dinner, but that is easy to understand from the sentence as a whole.

If you wanted to make it more explicit, you could say:

saat saya makan malam = when I was eating dinner

But the shorter version is very natural.

Indonesian does not mark tense the way English does.

There is no verb change like get / got / gotten. Time is often understood from context, or shown with time words such as:

kemarin = yesterday
tadi = earlier / just now
sudah = already

So terkena itself does not mean past tense. The English translation may use got because that sounds natural in context, but the Indonesian sentence is not grammatically marked as past.

Yes, but the meaning changes slightly.

kemeja = shirt, especially a collared or more shirt-like garment
baju = clothes / top / shirt, more general

So:

kemeja putih saya = my white shirt
baju putih saya = my white top/shirt/clothes item

If you specifically mean a shirt, especially a dress shirt or button-up shirt, kemeja is more precise.

It is natural and correct. It sounds neutral and fine.

A more conversational version might be:

Kemeja putih saya kena saus pedas waktu makan malam.

Differences:

kena is more casual than terkena
waktu is often more conversational than saat

But the original sentence is completely natural, especially in standard spoken or written Indonesian.

Usually, yes.

Terkena often suggests that something happened to the subject, often unintentionally. In this sentence, it sounds like the sauce accidentally got onto the shirt.

If you wanted to describe a more deliberate action, you would probably use a different structure, such as:

Saya menumpahkan saus pedas ke kemeja putih saya.
= I spilled spicy sauce onto my white shirt.

So terkena focuses more on the shirt being affected than on who caused it.