Learn Hardcore Portuguese (Portugal): Os dados acabaram no meu telemóvel, por isso vou usar a rede da biblioteca. - My mobile data ran out on my phone, so I’m going to use the library’s network.

Because os dados is the subject. Acabar here is intransitive: “the data ran out.” Eu acabei os dados would mean “I finished the data (files),” which sounds odd. You can also hear Acabaram-se os dados or Fiquei sem dados.

Why is the verb plural (acabaram) and not singular (acabou)?

Because dados is plural. Use singular if the subject is singular: O pacote de dados acabou / O saldo acabou.

What does no mean exactly?

It’s the contraction em + o → no. So no meu telemóvel = “on my phone.” Feminine is na = em + a.

Why no meu telemóvel and not do meu telemóvel?

Em (→ no) expresses location/context: “on my phone.” De (→ do) expresses possession: Os dados do meu telemóvel acabaram is also correct; it just uses a possessive structure.

Is telemóvel the same as celular?

Yes. Telemóvel is European Portuguese. In Brazil, people say celular. You may also hear telefone (more general). Common PT abbreviation: tlm.

Do I need to say dados móveis instead of just dados?

Not necessarily. In context, dados is understood as mobile data. To be explicit, say os dados móveis or o pacote de dados. Avoid os meus dados here—it can mean “my personal data/files.”

What are some natural alternatives a Portuguese person might say?

Fiquei sem dados (no telemóvel).
Acabaram-se os dados (no telemóvel).
Acabou-me o plafond de dados. (very PT-PT; “allowance”)
Já não tenho dados no telemóvel.

Why use por isso here? Could I use então or portanto?

por isso = “so/therefore,” neutral and very common.
então = informal/conversational connector.
portanto = more formal or written.
logo = rather formal/literary.
por isso é que = “that’s why,” adding emphasis to the cause.

Do I need a comma before por isso?

Yes, typically. It links two main clauses, so write “…, por isso …”. At sentence start: Por isso, vou usar…

Why da in da biblioteca?

da = de + a (of/from + the, feminine). biblioteca is feminine. With a masculine noun you’d use do = de + o (e.g., o Wi‑Fi do café).

Does rede mean Wi‑Fi? Could I say Wi‑Fi instead?

rede means “network” in general; with da biblioteca, it naturally refers to the library’s Wi‑Fi. It’s also very common to say o Wi‑Fi da biblioteca or a Internet da biblioteca.

Should it be vou usar or usarei?

In speech, the near future ir + infinitivo is preferred: vou usar. usarei is correct but sounds more formal/distant or for predictions.

Is vou a usar ever correct?

Not for the future. Use ir + infinitivo with no preposition: vou usar. ir a + infinitivo appears in other, specific expressions (e.g., fui a saber) and isn’t used here.

Could I say Vou ligar-me à rede da biblioteca?

Yes. ligar-se a = connect to. Note a + a → à: ligar-me à rede. Vou usar a rede focuses on using it; Vou ligar-me à rede focuses on connecting.

Can I replace the second clause with porque?

No. porque = because (introduces the cause). Your sentence expresses a result: “…, por isso …”. If you want porque, flip the order: Vou usar a rede da biblioteca porque os dados acabaram…

Is it usar a rede or usar da rede?

Usar takes a direct object: usar a rede. The da here marks possession (a rede da biblioteca), not the verb’s complement.

Do I have to include meu in no meu telemóvel?

In European Portuguese, possessives normally take the article: o meu telemóvel; after em, it’s no meu telemóvel. You can also hear no telemóvel when it’s obvious you mean your own phone.

Any quick pronunciation tips (European Portuguese)?

dados ≈ DAH-doosh (final s often like English bold sh).
acabaram with reduced vowels; final -m nasalizes: uh-kah-BAH-ruŋ.
telemóvel stress on mó: teh-luh-MAW-vel.
por isso often links: p’RIS-soo (the r carries over).
biblioteca: bee-blee-oo-TEH-kah (unstressed vowels reduced).