Learn Hardcore Indonesian: Dia mengunggah foto presentasi dan menghapus yang salah. - He/She uploads the presentation photos and deletes the wrong ones.

Dia means he or she; it’s gender-neutral. Context tells you which.
Ia is a more formal, written-style subject pronoun (e.g., Ia mengunggah...). You don’t normally use ia after prepositions.
Beliau is an honorific he/she for respected people.
Mereka = they (plural).

Do I need to repeat Dia before the second verb?

No. Indonesian commonly shares the same subject across coordinated verbs:

Natural: Dia mengunggah foto presentasi dan menghapus yang salah.
You can repeat for emphasis or clarity, but it’s usually unnecessary: Dia ... dan dia ... (grammatical but often redundant).

Why is it mengunggah and not unggah?

Unggah is the root. The active transitive form uses the prefix meN-, which becomes meng- before vowels, so you get mengunggah.
Similarly, hapus → menghapus.
Bare roots (unggah, hapus) are common in imperatives or headlines: Unggah fotonya sekarang. / Hapus file itu.

Is mengunggah the same as saying upload or mengupload? Which is better?

Mengunggah is the standard Indonesian form (preferred in writing and formal contexts).
Meng-upload/mengupload is very common in everyday speech and tech contexts; it’s informal/loanwordy.
Depending on context, you might also hear memasang (to post), memublikasikan (to publish), or mengirim (to send).

What does foto presentasi mean exactly? Which word modifies which?

In Indonesian, the head noun comes first and is modified by the noun after it. Foto presentasi = photo(s) of a presentation.
Presentasi foto would mean a photo-based presentation (a presentation consisting of photos).
If you mean photos for use in a presentation, foto untuk presentasi is explicit.

Does foto presentasi mean one photo or multiple photos? How do I show plural?

Indonesian doesn’t mark plural by default, so it can mean one or many. To show plural, use:

Does the sentence describe past time? How do I mark past or ongoing?

Verbs don’t conjugate for tense in Indonesian. Use particles/adverbs:

Does dan mean then? If I want sequence, what should I use?

Dan = and; it doesn’t inherently mark sequence (though context often implies it).
For explicit sequence, use lalu or kemudian: Dia mengunggah..., lalu/kemudian menghapus...

What does yang do in yang salah?

Yang turns an adjective or clause into a noun phrase (a headless relative).
Yang salah = the wrong one(s) / that which is wrong.
Without yang, menghapus salah is ungrammatical.
Don’t confuse with kesalahan (a mistake). Menghapus kesalahan means erase a mistake, not delete the wrong file/photo.

Is yang salah singular or plural?

It’s number-neutral. If you need to be explicit:

Why is foto omitted in the second clause? Is that normal?

Yes. Indonesian often drops repeated nouns when context is clear. Menghapus yang salah is shorthand for menghapus foto yang salah.

Could yang salah refer to something other than the photo? How do I clarify?

By default it refers to the most salient prior noun (here, foto). To disambiguate, say:

menghapus foto yang salah (the wrong photo)
menghapus presentasi yang salah (the wrong presentation) Adding itu/tersebut (e.g., yang salah itu) adds emphasis/definiteness but doesn’t itself specify which noun.

How do I negate the second action correctly?

Verb/adjective negation uses tidak: Dia mengunggah foto presentasi, tetapi tidak menghapus yang salah.
Bukan negates noun phrases or corrects identity/focus: Bukan yang salah yang dia hapus, melainkan yang benar.
“The right one” is yang benar.

How would a passive version look?

Several natural options:

Standard passive with enclitic agent: Foto presentasi diunggahnya dan yang salah dihapusnya.
With oleh: Foto presentasi diunggah oleh dia dan yang salah dihapus (olehnya).
“Short passive” (colloquial, no meN- on the verb): Foto presentasi dia unggah dan yang salah dia hapus.

How do I mention the platform or destination (to/at)?

Movement to a destination: ke → Dia mengunggah foto presentasi ke Google Drive.
On social media, both di (“on”) and ke (“to”) are heard: mengunggah di Instagram / mengunggah ke Instagram. For file storage, ke is usually clearer.

How do I make “the presentation photos” or “his/her presentation photos” explicit?

-nya often marks definiteness or possession:
- foto presentasinya = the presentation photo(s) / his/her presentation photo(s) (context decides).
To be unambiguously possessive, you can say foto presentasi dia or foto presentasinya (the latter is more natural).

Any quick pronunciation tips for mengunggah and yang?

mengunggah: roughly “muhng-OONG-gah”; ngg sounds like “ng” plus a hard g; final h is lightly audible.
yang: “yahng” (broad a as in “father”).