Wenn ich mich nicht irre, beginnt die Besprechung um halb neun.

In this sentence, wenn means if:

• Wenn ich mich nicht irre = If I’m not mistaken

German wenn can mean different things depending on context:

• if: Wenn es regnet, bleiben wir zu Hause.
• when/whenever for repeated situations: Wenn ich müde bin, trinke ich Kaffee.

For a one-time future when, German often uses wenn too, so learners have to rely on context. Here, the meaning is clearly if.

Because wenn introduces a subordinate clause, and in German subordinate clauses the finite verb usually goes to the end.

So:

• ich irre mich nicht = normal main-clause order
• wenn ich mich nicht irre = subordinate-clause order, with irre at the end

That is a very common pattern in German:

• weil ich müde bin
• dass er heute kommt
• wenn wir genug Zeit haben

Because the verb is sich irren, which means to be mistaken or to be wrong.

It is a reflexive verb, so it needs a reflexive pronoun:

• ich irre mich
• du irrst dich
• er irrt sich

In this sentence:

• Wenn ich mich nicht irre = If I am not mistaken

The reflexive pronoun here is mich, because it goes with ich.

Not exactly.

• sich irren usually means to be mistaken
• irren without the reflexive pronoun is less common in everyday speech and can sound more formal or literary; it can mean to err
• There is also sich verirren, which means to get lost

So in normal conversation, if you want to say to be mistaken, use sich irren.

Examples:

• Ich habe mich geirrt. = I was mistaken.
• Du irrst dich. = You’re mistaken.

Because German main clauses follow the verb-second rule.

The first position in the sentence is already occupied by the whole subordinate clause:

• Wenn ich mich nicht irre, ...

So the finite verb of the main clause must come next:

• beginnt

Then the subject comes after it:

• die Besprechung

So the structure is:

• Wenn ich mich nicht irre, beginnt die Besprechung um halb neun.

This is very typical in German:

• Wenn es regnet, bleiben wir zu Hause.
• Weil ich krank bin, komme ich nicht.

Yes, that is grammatically correct.

If you start with the main clause, you get normal main-clause word order:

• Die Besprechung beginnt um halb neun, wenn ich mich nicht irre.

That sounds natural too. The difference is mostly about emphasis:

• Starting with Wenn ich mich nicht irre puts the if I’m not mistaken part first
• Starting with Die Besprechung beginnt... puts the meeting time first

Yes. In German, a subordinate clause introduced by wenn is separated from the main clause by a comma.

So you must write:

• Wenn ich mich nicht irre, beginnt die Besprechung um halb neun.

This is a standard German punctuation rule.

It means at 8:30, not 9:30.

This is a very common point of confusion for English speakers.

In German:

• halb neun literally means half to nine
• so it is half an hour before nine
• therefore: 8:30

More examples:

• halb eins = 12:30
• halb fünf = 4:30
• halb zehn = 9:30

Also, um is used for clock times:

• um acht
• um 8:30
• um halb neun

Because Besprechung is a feminine noun in German.

Its article is:

• die Besprechung in the nominative singular

Here it is the subject of the main clause, so nominative is correct:

• die Besprechung beginnt

You may also see forms like:

• der Besprechung in the dative or genitive
• die Besprechung in the accusative singular as well

But in this sentence, it is nominative because the meeting is the thing that begins.

Beginnt is the 3rd person singular present tense form of beginnen.

Its basic forms are:

• beginnen = infinitive
• beginnt = he/she/it begins
• begann = simple past
• begonnen = past participle

In this sentence, the subject is singular:

• die Besprechung = the meeting

So the verb must also be singular:

• die Besprechung beginnt

Sometimes, yes.

• beginnen = to begin
• starten = to start

For a meeting, beginnen is usually the more neutral and standard choice:

• Die Besprechung beginnt um halb neun.

starten is also possible in some contexts, but it can sound a little more informal or more like something is being actively launched. For events and meetings, beginnen is usually the safest option.

Yes, very common.

It is a standard way to say:

• If I’m not mistaken
• If I remember correctly

It sounds natural and polite, especially when you are not completely certain.

Similar expressions include:

• Soweit ich weiß, ... = As far as I know, ...
• Wenn ich mich recht erinnere, ... = If I remember correctly, ...
• Ich glaube, ... = I think ...

In this sentence, nicht is in the natural position.

• Wenn ich mich nicht irre = if I’m not mistaken

Here nicht negates the idea of being mistaken.

If you moved it, the sentence would either become unnatural or change emphasis. So as a learner, it is best to remember this chunk as a fixed expression:

• Wenn ich mich nicht irre, ...

That will sound correct and idiomatic.