Learn Hardcore Turkish: Yarın seni kahveye davet ediyorum, uygunsan haber ver. - I’m inviting you for coffee tomorrow; let me know if you’re available.

Turkish often uses the present continuous to talk about near-future arrangements. With a time word like yarın, davet ediyorum means “I’m inviting (you) tomorrow,” i.e., a set plan.

More neutral/explicit future: davet edeceğim (I will invite).
Softer/polite desire: davet etmek istiyorum (I would like to invite).

Why is it seni and not sana?

Because davet etmek (“to invite”) takes the person invited in the accusative case.

Person (direct object): seni = you (accusative)
Goal/purpose (often dative): e.g., kahveye
Compare:
Correct: Seni kahveye davet ediyorum.
Incorrect: Sana davet ediyorum. (You can say: Sana davetiye gönderiyorum = I’m sending you an invitation.)

What does kahveye mean here, and why the -e?

Kahveye is the dative case of kahve (coffee), formed as kahve + y + e; the -y- is a buffer consonant. The dative (-e/-a) often marks direction, goal, or purpose. Here, it means “for/to coffee” (an occasion).

If you want to be explicit about the activity: kahve içmeye (to drink coffee).

Why not kahvede or kahve için instead of kahveye?

Kahvede (-de = locative) means “at the coffee(-house).” It describes a location, not an invitation goal.
Kahve için (“for coffee”) is grammatical but less idiomatic in this invite formula.
Most natural invitations are:
Seni kahveye davet ediyorum.
Seni kahve içmeye davet ediyorum.

Exactly what does uygunsan mean and how is it formed?

It means “if you are available/suitable.”
Formation: uygun + sa (if) + n (you) = uygunsan.
Compare: uygunsa = “if it is suitable/appropriate (in general),” not specifically “if you are.” For availability, many speakers prefer müsaitsen (“if you’re free/available”).

Is müsaitsen better than uygunsan here?

Both work, but they’re slightly different in nuance:

müsaitsen = if you’re free/available (very common in scheduling)
uygunsan = if it’s suitable for you / if it works for you In invites, müsaitsen sounds especially natural.

What does haber ver literally mean, and how is it used?

Literally “give news,” but idiomatically “let me know / get back to me.” It’s a common set phrase. Without an explicit indirect object, “to me” is understood from context. You can add it:

Bana haber ver. (Let me know.)

Is haber ver polite enough? How can I soften it?

Haber ver is direct/informal (2nd singular imperative). To soften or be more polite:

Add please: Lütfen haber ver.
Use request forms: Haber verir misin?, Lütfen bana haber verir misin?
For formal/plural: Lütfen bana haber verir misiniz?

Is the comma between the clauses necessary? Could I use eğer?

You can punctuate either as in the original or as: Uygunsan, haber ver. A comma after the if-clause is common but not mandatory in casual writing.
Using eğer is also fine for emphasis: Eğer uygunsan, haber ver.

Can I change the word order, like Seni yarın kahveye davet ediyorum?

Yes. Turkish allows flexible word order for emphasis:

Yarın seni kahveye davet ediyorum (neutral: time first)
Seni yarın kahveye davet ediyorum (emphasizes “you”)
Kahveye yarın seni davet ediyorum (heavier focus on “to coffee” and “you”) Meaning stays; emphasis shifts.

Is it one word or two: davet ediyorum?

Two words. Davet etmek is a compound verb formed with the light verb etmek. Conjugation attaches to et-: davet ediyorum, davet edersin, davet ettik, etc. Don’t write it as one word.

Why is it ediyorum and not etiyorum?

With vowel-initial suffixes (like -iyor), the t in et- commonly voices to d: ediyorum, ediyorsun, ediyor. This is a regular sound change in many -etmek compounds.

Does kahveye mean the drink or the place?

Colloquially, kahveye (davet etmek) implies “for a coffee (occasion).” It can be understood as the activity rather than a physical “coffeehouse.” For clarity:

Activity: kahve içmeye (to drink coffee)
Place: kafeye (to the café), kahvehaneye (to the traditional coffeehouse)

How do I make the whole sentence formal/respectful?

Use plural/formal “you” and polite requests:

Yarın sizi kahveye davet ediyorum, uygunsanız (veya müsaitseniz) lütfen bana haber verir misiniz? Even more formal: … bilgilendirir misiniz? or … beni haberdar eder misiniz?

How do I make it more casual?

Options:

Yarın kahveye gelsene. (Come for coffee tomorrow, won’t you?)
Yarın kahve içelim mi? (Shall we have a coffee tomorrow?)
Yarın kahve? Müsaitsen haber ver.

Would using the future (davet edeceğim) change the meaning?

Slightly.

davet ediyorum: arrangement already in motion / planned schedule.
davet edeceğim: a statement of future intention or a decision (often made now). Both are fine with yarın; choose for nuance.

Where does bana go in haber ver, and is beni ever correct there?

Use dative bana (“to me”), since you “give news to me”:

Uygunsan bana haber ver. / Bana uygunsan haber ver. Avoid beni haber ver (wrong). If you use another verb, accusative can appear: Beni haberdar et. (Inform me.)

Can I drop seni?

Only if context already makes it crystal clear who is being invited. Seni is the direct object; without it, davet ediyorum is incomplete/ambiguous. In practice, keep seni unless the addressee is obvious.

How would I ask “Are you available tomorrow (for coffee)?” instead?

Availability: Yarın müsait misin? (informal) / Yarın müsait misiniz? (formal)
With coffee: Yarın kahve içmeye müsait misin(iz)? or Yarın kahveye müsait misin(iz)? Both are used; içmeye is clearer about the activity.

Is there any difference between using haber ver and more formal verbs?

Yes. Register shifts:

Informal/common: haber ver, bana haber ver
Neutral/formal: haber verir misin(iz)?
Formal: beni haberdar et(mez misin/ misiniz)?, beni bilgilendir(ebilir misin/ misiniz)?