Learn Hardcore Turkish: Yeni mahalleliyle tanıştıktan sonra birlikte kahve içtik. - After meeting the new local resident, we had coffee together.

It’s the comitative/instrumental suffix -le/-la meaning “with.” Because mahalleli ends in a vowel, a buffer y appears: mahalleli + y + le → mahalleliyle. Vowel harmony picks -le (front vowel), not -la.

Can I write ile separately instead of using the suffix?

Yes. Both mahalleliyle and mahalleli ile are acceptable in writing. Even when written separately, it’s pronounced as if merged. After a vowel, you’ll still hear a glide [y].

Does yeni mahalleli really mean “the new neighbor”? Would komşu be better?

mahalleli = a (local) resident of the neighborhood; it can refer to a single person or the neighborhood folks collectively.
For “neighbor,” komşu is more common and natural.
So many would prefer: Yeni komşuyla or, more idiomatically, Yeni komşumuzla (“with our new neighbor”).

Could Yeni mahalleliyle be misunderstood as a place name?

Potentially. Yeni Mahalle is a common neighborhood name in Turkey. If you meant “a person from Yeni Mahalle,” you’d capitalize: Yeni Mahalleli. In your sentence, the lowercase yeni mahalleli is read as “new resident of the neighborhood.”

Why is kahve not kahveyi?

Because the coffee is indefinite/generic: “we drank coffee / we had coffee.” If you mean a specific, known coffee, use accusative: kahveyi içtik = “we drank the coffee.”

How is tanıştıktan sonra formed, exactly?

Verb: tanış- “to meet (get acquainted)”
Suffix: -DIK + Ablative (-DAn) → “after doing”
Voicing assimilation: d → t after the voiceless ş
Result: tanış + dık + tan → tanıştıktan
Add sonra (“after”) → tanıştıktan sonra = “after (we) met.”

Who is understood to be the subject of tanıştıktan sonra?

By default, it shares the subject with the main clause. Here, the subject is “we,” so it means “after we met.” If you want a different subject, say it: O yeni mahalleliyle tanıştıktan sonra biz kahve içtik (“After he met the new neighbor, we drank coffee”) or use a nominalization: Onun yeni mahalleliyle tanışmasından sonra…

What does birlikte add? Is it necessary?

Birlikte = “together.” Without it, the sentence could be read as “After meeting the new neighbor, we drank coffee,” possibly implying together but not guaranteeing it. Birlikte makes the togetherness explicit.

Where can I place birlikte?

Common options:

… sonra birlikte kahve içtik (neutral)
… sonra kahveyi birlikte içtik (emphasis on doing it together)
End-placement (… kahve içtik birlikte) is possible for emphasis, but less neutral.

Do I have to use ile with tanışmak?

Yes, to express meeting someone, use biriyle tanışmak (“to meet someone”). Don’t say birini tanışmak. Note: birini tanımak = “to know (be acquainted with) someone,” which is different.

Why is there no pronoun for “we”?

Turkish marks the subject on the verb. iç-ti-k = drank-Past-1pl → “we drank.” The pronoun biz is only used for emphasis or clarity.

How flexible is the word order here?

Quite flexible. The time clause often comes first:

Yeni mahalleliyle tanıştıktan sonra birlikte kahve içtik (neutral)
Yeni mahalleliyle tanıştıktan sonra kahveyi birlikte içtik (definite coffee, emphasis on togetherness)
Keep the finite verb içtik at the end for the most natural style.

Are there alternative ways to say “after we met”?

Tanışınca = “when (we) met” (general temporal)
Tanışıp sonra = “(we) met and then …” (sequence)
Tanışır tanışmaz = “as soon as we met” (immediacy)
All are grammatical; pick for nuance.

How can I explicitly say “with our new neighbor”?

Use a possessive: Yeni komşumuzla tanıştıktan sonra… This is the most idiomatic way to say “after meeting our new neighbor.”

Could I say “a coffee” instead of generic coffee?

Yes: bir kahve içtik ≈ “we had a coffee (each).” Plural kahveler içtik is possible but less common unless you mean multiple cups or emphasize quantity.