Wir treffen uns im Club.

In German, sich treffen is a very common reflexive expression meaning to meet up or to meet each other.

So:

• Wir treffen uns = We are meeting / We meet up
• literally: We meet ourselves
• natural meaning: We meet each other

Without uns, treffen usually needs a direct object:

• Wir treffen Anna. = We meet Anna.
• Ich treffe meinen Lehrer. = I meet my teacher.

So in your sentence, uns shows that the people in wir are meeting one another.

The base form is sich treffen.

That is how reflexive verbs are usually listed in dictionaries:

• sich treffen = to meet up / to meet each other

In the sentence:

• wir = subject
• treffen = verb form for wir
• uns = reflexive pronoun matching wir

The full pattern is:

• ich treffe mich
• du triffst dich
• er/sie/es trifft sich
• wir treffen uns
• ihr trefft euch
• sie/Sie treffen sich

Im is just the contraction of in dem:

• in dem → im

So:

• im Club = in dem Club

This contraction is extremely common and usually preferred in normal German.

Here, dem is used because Club is masculine:

• der Club
• dative: dem Club

So im Club literally means in the club.

Club is in the dative case.

After the preposition in, German uses:

• dative for location (where?)
• accusative for direction/movement (where to?)

Here, the sentence describes a location:

• Wir treffen uns im Club. = We are meeting in/at the club.

So it uses dative.

Compare:

• Wir sind im Club. = We are in the club. (location)
• Wir gehen in den Club. = We are going into the club. (movement toward)

It can often mean either, depending on context.

In natural English, you might translate it as:

• in the club
• at the club

German im Club literally means in the club, but in many situations English prefers at the club.

So if the meaning shown to the learner is We’re meeting at the club, that is perfectly natural.

Because all nouns are capitalized in German.

So:

• wir = not capitalized
• treffen = not capitalized
• uns = not capitalized
• Club = capitalized, because it is a noun

This is one of the most noticeable spelling differences between German and English.

This is normal German main-clause word order:

• Wir = position 1
• treffen = position 2
• uns = after the verb
• im Club = place expression at the end

German main clauses usually put the conjugated verb in second position:

• Wir treffen uns im Club.
• Heute treffen wir uns im Club.
• Im Club treffen wir uns heute.

The verb treffen stays in second position in each main clause.

Yes. Very often, German uses the present tense for planned future events.

So:

• Wir treffen uns im Club.

can mean:

• We meet at the club.
• We’re meeting at the club.
• We will meet at the club.

The exact time meaning depends on context. If this is about an arrangement, English often uses We’re meeting at the club.

There is an important difference:

• Wir treffen uns. = We meet up / We meet each other.
• Wir treffen ... = We meet ... / We hit ... something or someone

Examples:

• Wir treffen uns morgen. = We’re meeting tomorrow.
• Wir treffen unsere Freunde morgen. = We’re meeting our friends tomorrow.
• Wir treffen das Ziel. = We hit the target.

So uns changes the meaning to a reflexive, mutual action.

Yes, it is grammatically correct, because im = in dem.

But in normal everyday German, im Club sounds much more natural.

Use in dem Club only when you want extra emphasis or contrast, for example:

• Nicht in der Bar, sondern in dem Club nebenan.

In most ordinary sentences, learners should prefer im Club.

Because the sentence describes where the meeting happens, not movement into the club.

• im Club = in the club / at the club → location → dative
• in den Club = into the club → direction → accusative

Compare:

• Wir treffen uns im Club. = We’re meeting at the club.
• Wir gehen in den Club. = We’re going into the club.

That location-vs-direction distinction is very important with in.

Yes. Club is commonly used in German and is understood as a normal noun.

You may also see the spelling Klub, but Club is very common.

The noun is masculine:

• der Club
• im Club
• einen Club

So even though it originally came from another language, it behaves like a regular German noun.