Learn Hardcore German: Wir treffen uns in dreißig Minuten im Park. - We will meet in thirty minutes in the park.

German uses a reciprocal reflexive with treffen when people meet each other. Wir treffen uns literally means “we meet ourselves,” but idiomatically it’s “we meet each other.” Without uns, Wir treffen is incomplete or can mean “we hit.” If you omit uns, you must name a direct object: Wir treffen Maria (We’re meeting Maria).

What’s the difference between jemanden treffen and sich treffen?

jemanden treffen = to meet someone (transitive): Wir treffen Anna im Park.
sich treffen = to meet each other (reciprocal): Wir treffen uns im Park. Use the reflexive when no specific direct object is named and the meeting is mutual.

Is the present tense here talking about the future? Why not Wir werden uns treffen?

Yes. German commonly uses the present tense with a time expression to talk about the near future. Wir treffen uns in dreißig Minuten is the most natural everyday choice. Wir werden uns in dreißig Minuten treffen is correct but sounds more formal or emphatic and is used less in casual speech when the time is already clear.

Why is it im Park and not in den Park?

Because you’re describing a location, not movement. In is a two-way preposition:

Location (Wo? where) → dative: im Park (in dem Park).
Direction (Wohin? where to) → accusative: in den Park (into the park).

What does im stand for, and what case is Park here?

im is the contraction of in dem. Park is masculine; with location you use the dative: in dem Park → im Park. Compare:

im Park = in the park (dative, location)
in den Park = into the park (accusative, direction)

For time, is in dative or accusative? Why in dreißig Minuten?

Temporal in normally takes the dative. You see it clearly with articles:

in einem Monat, in einer Stunde (dative) With bare plurals, the form looks the same: in dreißig Minuten (dative plural). With an adjective, you’ll see the dative plural article: in den nächsten dreißig Minuten.

Is the order in dreißig Minuten im Park fixed? Could I swap them?

The default, natural order is Time → Place: in dreißig Minuten im Park. You can swap for emphasis or style:

Wir treffen uns im Park in dreißig Minuten. (slightly emphasizes the place)
Im Park treffen wir uns in dreißig Minuten. (fronting the place) All are correct as long as the conjugated verb stays in position 2 in main clauses.

Could I say am Park or auf dem Park instead of im Park?

am Park (an dem) = at/by the park (near its edge), not inside.
im Park (in dem) = inside the park.
auf dem Park is not used with Park. auf is for surfaces or certain locations like auf dem Markt, auf dem Spielplatz. For a park, use im Park.

How do I turn this into a suggestion like “Let’s meet in 30 minutes in the park”?

Two natural options:

Yes–no question as a proposal: Treffen wir uns in dreißig Minuten im Park?
With lassen (let’s): Lass uns uns in dreißig Minuten im Park treffen. This is grammatically correct, but the double uns sounds clunky; many speakers prefer the first option or rephrase, e.g. Lass uns in dreißig Minuten in den Park gehen.

What’s the difference between in dreißig Minuten and nach dreißig Minuten?

in dreißig Minuten = thirty minutes from now (a point in the future).
nach dreißig Minuten = after thirty minutes (once that duration has elapsed, often relative to another event). Also useful: innerhalb von dreißig Minuten = within thirty minutes (at any time up to that limit).

Is the spelling dreißig mandatory? What about dreissig?

In Germany and Austria, standard spelling is dreißig with ß (after a long vowel/diphthong). In Switzerland and Liechtenstein, ß isn’t used; dreissig is standard there. Both are understood; use dreißig unless you follow Swiss orthography.

Can I write numerals instead of the word, like in 30 Minuten?

Yes. In 30 Minuten is perfectly fine in everyday writing. In formal prose, many style guides prefer spelling out smaller numbers, but practices vary.

Why are Minuten and Park capitalized, but dreißig isn’t?

All German nouns are capitalized: Minute, Park. Adjectives and numbers written as words are lower-case unless they start a sentence.

Any pronunciation tips for this sentence?

treffen has a short e (like “treh-” not “tree-”); the double ff signals a short vowel.
ß sounds like a sharp s (same as ss).
dreißig: final -ig is commonly pronounced like the “ch” in German ich (some regions say it like “ik”).
Minuten: stress the second syllable (mi-NU-ten).
Park: the a is like the a in “father”; final k is crisp.

What’s the difference between Wir sehen uns and Wir treffen uns?

Wir sehen uns = We’ll see each other; often a casual “See ya,” and it doesn’t necessarily imply a planned meeting.
Wir treffen uns = We’re meeting (by arrangement). Your sentence expresses a concrete plan.

Where does uns go if I change the sentence structure (questions or subordinate clauses)?

Yes–no question: Treffen wir uns in dreißig Minuten im Park?
W-question: Wann treffen wir uns im Park? / Wo treffen wir uns in dreißig Minuten?
Subordinate clause: …, dass wir uns in dreißig Minuten im Park treffen. The reflexive uns stays before the verb at the end.