Learn Hardcore Portuguese (Brazil): Este ambiente silencioso é perfeito para terminar relatórios. - This quiet environment is perfect to finish reports.

Este is a demonstrative adjective meaning “this” and refers to something close to the speaker.
Esse (“that”) usually points to something near the listener or previously mentioned, and aquele (“that over there”) refers to something distant from both speaker and listener.

Why is ambiente masculine, and why is the adjective silencioso also masculine?

In Portuguese every noun has a gender. Ambiente is grammatically masculine, so any adjective describing it must agree in gender (and number), hence silencioso (masculine) rather than silenciosa (feminine).

What’s the difference between é and está here? Why not use está silencioso?

É is from the verb ser, used for inherent or defining qualities. Saying é silencioso treats the quietness as a characteristic of the environment. Está (from estar) would imply a temporary state (e.g., Este ambiente está silencioso hoje – “This environment is quiet today”).

Why is it perfeito para terminar relatórios and not a gerund like terminando relatórios?

After para (meaning “in order to” or simply “to”), Portuguese uses the infinitive (terminar). The gerund (terminando) describes an ongoing action, not the purpose or function.

Why is there no article before relatórios? Could I say os relatórios?

Without an article, relatórios has a general sense: “reports” in general. If you refer to specific reports already known, you can say para terminar os relatórios (“to finish the reports”).

Can I swap terminar for concluir or acabar? What about acabar de?

Yes, concluir relatórios is a direct synonym and works fine. Acabar relatórios is less idiomatic; instead, acabar de + infinitive means “to have just finished,” as in Acabei de terminar o relatório (“I just finished the report”).

Is it possible to change the word order, for example: Este é o ambiente perfeito e silencioso para terminar relatórios?

Yes. Portuguese allows some flexibility. Placing silencioso after perfeito (and adding e) shifts the emphasis slightly, making “perfect” the main descriptor and “quiet” an additional comment, rather than a single combined idea.

Why is there no um before ambiente? Could I say Este é um ambiente silencioso ...?

You could. Este é um ambiente silencioso means “This is a quiet environment,” introducing it among other possible environments. The original sentence drops the article to present the noun phrase directly (“This quiet environment is perfect...” rather than “This is a quiet environment...”).

How do you pronounce ambiente silencioso, and where are the stresses?

In Brazilian Portuguese:

ambiente: /ɐ̃.bi.ˈẽ.tʃi/ (stress on the second syllable)
silencioso: /si.lẽ.si.ˈo.zu/ (stress on the penultimate syllable “o”)
Vowels are generally clear and each syllable tends to be pronounced distinctly.