Learn Hardcore Romanian: Noi mergem la un restaurant liniștit diseară. - We are going to a quiet restaurant tonight.

No. Romanian verbs carry endings that show the subject. Mergem ends in -em, which marks first person plural (“we”), so you can omit Noi unless you want to add emphasis:
– Noi mergem… (stressed “we are going”)
– Mergem… (neutral “we are going”)

Why is mergem in the present tense when the plan is for tonight?

In Romanian, the simple present is often used for near‐future events (just like English “I’m meeting him tomorrow”). It’s very common in speech. If you want to be explicitly in the future tense, you can say vom merge:
– Mergem diseară la…
– Vom merge diseară la…

What does la mean in la un restaurant? Why not use în?

La expresses movement to a place (a restaurant, the cinema, school etc.). Using la is the standard way to say “to [that place]”:
– la restaurant – to the restaurant
By contrast, în would mean “into/inside”:
– mergem într-un restaurant – we go inside a restaurant (less idiomatic for “we’re going to eat there”)

Why is the indefinite article un used before restaurant? When do I use un vs o?

Romanian indefinite articles agree in gender and number:
– un for masculine singular (e.g. un restaurant, un băiat)
– o for feminine singular (e.g. o casă, o fată)
There is no indefinite article for plural; you’d just say restaurante (restaurants).

Why is the adjective liniștit placed after restaurant? Can I put it before?

The default adjective order in Romanian is noun + adjective. So you normally say restaurant liniștit. Placing the adjective before the noun (e.g. un liniștit restaurant) is grammatically possible but sounds poetic or emphatic.

How does liniștit agree with restaurant? Why is it not liniștită?

Adjectives match the gender and number of the nouns they describe. Restaurant is masculine singular, so the adjective is liniștit (masculine singular). If you had a feminine noun you would use liniștită (e.g. o cameră liniștită).

What does diseară mean, and why is it at the end of the sentence?

Diseară means this evening or tonight. Adverbs of time in Romanian can go at the start or the end of a sentence. Putting diseară at the end is very natural:
– Noi mergem la un restaurant liniștit diseară.
You could also front it:
– Diseară mergem la un restaurant liniștit.

Can I say astă seară, seara asta, or în seara asta instead of diseară?

Yes. All these mean “this evening,” with slight style differences:
– diseară (one‐word adverb) – neutral, common
– astă seară / seara asta (noun + demonstrative) – more colloquial
– în seara asta (prepositional phrase) – emphasizes “in the course of this evening”

Could I also use the future tense for diseară? For example, Noi vom merge diseară la un restaurant liniștit?

Absolutely. Using vom merge makes the future explicit:
– Noi mergem diseară… (present for near future)
– Noi vom merge diseară… (future tense)
Both are correct; the difference is style and clarity rather than strict grammar.

How are the Romanian letters ă, ș, and ț pronounced in this sentence?

– ă is a mid‐central vowel [ə], like the a in “sofa.”
– ș is [ʃ], like sh in “ship.”
– ț is [ts], like ts in “cats.”
So diseară is [di‐se‐ə‐rə], and liniștit is [li‐niʃ-tsit].