Learn Hardcore Indonesian: Dia merasa canggung saat presentasi pertama, tapi cukup tersenyum agar suasana tidak tegang. - He/She feels awkward during the first presentation, but just needs to smile so that the atmosphere is not tense.

Dia is a gender‑neutral third person singular pronoun. It can mean he, she, or even they (singular) depending on context.
In this single sentence, there is no grammatical marker that tells you the gender; you would need previous context (earlier sentences or situation) to know whether dia is male or female. Without that, dia is simply “that person” (he/she).

Why do we say merasa canggung instead of just canggung? Are both correct?

Merasa canggung literally means to feel awkward. Using merasa emphasizes the internal feeling or subjective experience.
You can also say Dia canggung saat presentasi pertama, and it is still grammatically correct and natural; here canggung works as a predicate adjective (“is awkward”).
The difference is very subtle:

Dia merasa canggung = focuses slightly more on the feeling.
Dia canggung = describes their state/quality as awkward in that situation.

What exactly does canggung mean? Is it like nervous, shy, or awkward?

Canggung most directly corresponds to awkward. It can describe:

Social awkwardness (not knowing how to act or what to say).
Physical awkwardness (moving in a stiff, unnatural way).
Often, in performance or presentation contexts, canggung overlaps with feeling stiff, self‑conscious, or not relaxed, which can include being a bit nervous, but it is not a direct synonym of gugup (nervous).

What is the difference between saat, ketika, and waktu in a sentence like saat presentasi pertama?

All three can mean when or at the time (of), but they differ slightly in feel and usage:

Saat: very common and neutral. Works well in spoken and written Indonesian.
- Dia merasa canggung saat presentasi pertama.
Ketika: a bit more literary/formal, often used in narratives and written text.
- Dia merasa canggung ketika presentasi pertama.
Waktu: originally “time”, but also used as “when” in everyday speech; can sound slightly more casual.
- Dia merasa canggung waktu presentasi pertama.

In this sentence, you can substitute saat, ketika, and waktu without changing the meaning much; saat is a very natural choice.

Why is it presentasi pertama and not presentasi yang pertama? Is there a difference?

Presentasi pertama literally means first presentation; the adjective pertama directly modifies presentasi. This is the most common and natural way to say first presentation.
Presentasi yang pertama is also grammatically correct, but it sounds a bit more specific or contrastive, like the one that was first (e.g., if you are comparing several presentations).
In everyday speech, for something like a person’s first‑ever presentation, presentasi pertama is what people usually say.

There is no word for his/her in presentasi pertama. How do Indonesians understand that it is “his/her first presentation”?

Indonesian often omits possessive pronouns when the owner is obvious from context. Here, since the sentence starts with Dia, the listener naturally understands that presentasi pertama refers to his/her first presentation.
If you really want to make the possessive explicit, you can say:

presentasi pertamanya (literally “his/her first presentation”)
But it is not necessary; the shorter presentasi pertama is completely natural.

What is the nuance of tapi in tapi cukup tersenyum? Is there a difference between tapi and tetapi?

Tapi and tetapi both mean but; tapi is more informal/colloquial, while tetapi is more formal and common in writing.
In spoken Indonesian, tapi is extremely frequent and sounds perfectly natural here. A more formal version of the sentence might use tetapi instead:

… tetapi cukup tersenyum agar suasana tidak tegang.

What does cukup mean in cukup tersenyum? Does it literally mean enough here?

Cukup basically means enough, sufficiently, or quite. In cukup tersenyum, it suggests that just smiling (not doing much else) was sufficient to achieve the effect.
So it has a nuance like he/she just smiled enough / simply smiled so that the atmosphere wouldn’t become tense.
Grammatically, cukup here is an adverb modifying tersenyum (to smile).

Why is it tersenyum and not just senyum? What does the prefix ter- do in this word?

The base word is senyum (smile). As a verb, Indonesian often uses tersenyum, which means to smile. Here, ter- does not mean “accidental” or “completed” like in some other verbs; it’s just part of the standard verb form “to smile”.
You can also see senyum used as a verb in more casual speech, especially in some regions or informal styles:

Dia senyum saja. (He/She just smiled.)
But Dia tersenyum is the more neutral, standard form.

What does agar mean, and how is it different from supaya or untuk in agar suasana tidak tegang?

Agar introduces a purpose or desired result, so agar suasana tidak tegang means so that the atmosphere wouldn’t be tense.

Agar and supaya are very similar; both mean so that / in order that. Supaya is often slightly more informal or conversational, but both are common.
Untuk usually means for / in order to and is followed by a verb or noun, not a full clause with its own subject and predicate.
So:
agar/supaya suasana tidak tegang (clause)
untuk menenangkan suasana (for calming the atmosphere)

In the part agar suasana tidak tegang, what is the subject of the clause?

In agar suasana tidak tegang, the subject is suasana (the atmosphere).
The structure is:

suasana (subject)
tidak tegang (predicate = “not tense”)
So the purpose clause literally means so that the atmosphere (suasana) is not tense.

What does suasana mean here? Is it more like atmosphere, mood, or environment?

Suasana can mean atmosphere, mood, or ambience depending on context. In this sentence, it refers to the general feeling or mood in the room/audience during the presentation.
So suasana tidak tegang is like saying the atmosphere is not tense or the mood isn’t tense. Both translations capture the idea.

Can I replace saat with selama in saat presentasi pertama? Would selama presentasi pertama be correct?

Yes, selama presentasi pertama is grammatically correct, but there is a slight nuance difference:

saat presentasi pertama = at the time of the first presentation (focus can be on the moment or period, quite general).
selama presentasi pertama = during the first presentation (emphasizes the whole duration of that presentation).
In this context, both make sense, but saat is a bit more neutral and slightly more common for this kind of general time reference.