Learn Hardcore Indonesian: Saat terlalu banyak tugas, saya merasa stres dan sulit tidur. - When there are too many assignments, I feel stressed and find it hard to sleep.

saat and ketika are very similar and usually interchangeable in this kind of sentence:
- Saat terlalu banyak tugas, ...
- Ketika terlalu banyak tugas, ...

Both sound natural.

waktu can also mean when in informal speech:
- Waktu terlalu banyak tugas, ...

Nuance:

saat and ketika feel a bit more neutral or slightly formal.
waktu is often more casual, especially in spoken Indonesian.

All three can introduce a time clause (when X happens, Y happens). In many everyday contexts, you can switch them without changing the meaning much.

Why is there no subject after saat? Should it be saat saya punya terlalu banyak tugas?

The full, very explicit version would be something like:

Saat saya punya terlalu banyak tugas, ...
Saat saya memiliki terlalu banyak tugas, ...

In Indonesian, it’s very common to omit elements that are obvious from context, especially in subordinate clauses (like the when clause).

Here:

The subject saya is the same in both parts of the sentence.
The meaning when I have too many tasks is clear.

So Indonesians often shorten it to:

Saat terlalu banyak tugas, ...

You can think of it as shorthand for Saat (saya punya) terlalu banyak tugas, .... It’s natural and grammatical.

Why is there no verb like punya (have) or ada (there is) in saat terlalu banyak tugas?

Indonesian often drops the verb of possession or existence when the meaning is clear.

More explicit versions would be:

Saat saya punya terlalu banyak tugas – when I have too many tasks.
Saat ada terlalu banyak tugas – when there are too many tasks.

But in context, saat terlalu banyak tugas is understood as when there are too many tasks (for me) or when I have too many tasks.

So:

The verb punya / ada / memiliki is understood.
Leaving it out makes the phrase shorter and sounds natural in everyday Indonesian.

What is the difference between terlalu banyak and just banyak?

banyak tugas = many tasks / a lot of tasks (neutral)
terlalu banyak tugas = too many tasks (more than is good or comfortable)

terlalu adds a negative / excessive meaning, similar to English too in too many or too much.

Compare:

Saya punya banyak tugas. – I have a lot of tasks. (just a fact)
Saya punya terlalu banyak tugas. – I have too many tasks. (implies a problem)

What exactly does tugas mean? Is it homework, work tasks, or something else?

tugas is a general word meaning task, assignment, duty. The exact meaning depends on context:

At school/university: often homework / assignment.
At work: work tasks / assignments / responsibilities.
In general: any kind of duty or task you’re responsible for.

So in this sentence, tugas could be:

school assignments,
office tasks,
or a mix of responsibilities in your life.

Context (for example mentioning school, work, etc.) would clarify it in real conversation.

Why do we say merasa stres? Could we just say saya stres?

Both are possible, with slightly different nuances:

Saya stres.
= I am stressed.
Simple, direct statement of your condition.
Saya merasa stres.
= I feel stressed.
Emphasizes the subjective feeling.

merasa means to feel. Adding it can:

sound a bit more reflective or descriptive,
make the sentence feel slightly more formal or careful.

In everyday speech, Saya stres is very common and perfectly natural. Saya merasa stres is also common and maybe a bit more formal or thoughtful.

Why is there no word for am (like I am) before stres? Isn’t something missing?

Indonesian does not use a verb like English “to be” (am/is/are) before adjectives or many nouns in simple present sentences.

So:

English: I am stressed.
Indonesian: Saya stres. (no verb needed)

Similarly:

Dia lapar. – He/She is hungry.
Mereka capek. – They are tired.

In your sentence, merasa is the main verb:

saya merasa stres = I feel stressed.

There is no need for a separate word meaning am.

Why is it dan sulit tidur and not dan saya sulit tidur?

In Indonesian, when the subject stays the same, you can omit it in the second part of the sentence.

The full version would be:

Saat terlalu banyak tugas, saya merasa stres dan saya sulit tidur.

Because saya is already clearly the subject, Indonesian speakers usually shorten it to:

... saya merasa stres dan sulit tidur.

You can understand it as:

... saya merasa stres dan (saya) sulit tidur.

Repeating saya is grammatically okay, but it often sounds a bit heavy or redundant in casual speech.

What is the difference between sulit and susah here?

Both sulit and susah can mean difficult and are often interchangeable:

sulit tidur ≈ susah tidur = have trouble sleeping.

Nuance:

sulit can sound slightly more neutral or formal.
susah is often more colloquial, very common in everyday speech.

In this sentence, either is fine:

Saya merasa stres dan sulit tidur.
Saya merasa stres dan susah tidur.

Both sound natural.

Is tidur a verb or a noun here? How should I understand sulit tidur?

Here, tidur functions as a verb: to sleep.

sulit tidur literally = difficult to sleep, which in natural English is have trouble sleeping.

A few similar patterns:

sulit makan – hard to eat / have difficulty eating.
sulit fokus – hard to focus.

So you can read sulit tidur as it is difficult (for me) to sleep or I have difficulty sleeping.

Can I say Saat saya terlalu banyak tugas instead? It feels closer to English.

Saat saya terlalu banyak tugas is not natural Indonesian.

If you want saya directly there, you need a more complete structure, for example:

Saat saya punya terlalu banyak tugas, ...
Saat tugas saya terlalu banyak, ...
Saat saya mendapat terlalu banyak tugas, ...

The pattern [pronoun] terlalu banyak [noun] usually needs a verb or some linking structure. That’s why saat terlalu banyak tugas (with the verb understood) is better than saat saya terlalu banyak tugas.

How do we know if this sentence is about the past, present, or future?

Indonesian doesn’t mark tense (past/present/future) with verb changes like English does. The sentence:

Saat terlalu banyak tugas, saya merasa stres dan sulit tidur.

can mean:

when I have too many tasks (in general / habitually),
when I had too many tasks (in the past),
when I will have too many tasks (in the future),

depending on context.

To be more specific, Indonesians usually add time words:

Past:
Dulu, saat terlalu banyak tugas, saya merasa stres dan sulit tidur.
(In the past, when I had too many tasks...)
Present (habit):
Sekarang, saat terlalu banyak tugas, saya merasa stres dan sulit tidur.
(Now, when I have too many tasks...)
Future:
Nanti, saat terlalu banyak tugas, saya pasti merasa stres dan sulit tidur.
(Later, when I have too many tasks, I will surely feel stressed...)

Is saya the only option for I here? What about aku or others?

saya is a neutral, polite pronoun for I, suitable in most situations, including:

talking to strangers,
at work,
in writing.

Other options:

aku – more informal / intimate, used with friends, family, or people of the same age.
gua / gue, ane, etc. – regional / slang forms (Jakarta, Betawi, etc.), very informal.

You could say:

Aku merasa stres dan sulit tidur.
in a casual context.

The grammar of the sentence doesn’t change; only the register / level of formality changes with the pronoun.