Bevor die Videokonferenz beginnt, schreibe ich noch schnell in den Gruppenchat.

Because bevor introduces a subordinate clause. In German, the conjugated verb usually goes to the end of a subordinate clause.

• Bevor die Videokonferenz beginnt
• literally: Before the video conference begins

This is one of the most important German word-order patterns to learn.

Because the sentence begins with the subordinate clause, and that whole clause takes up position 1 in the sentence. In a German main clause, the conjugated verb must come in position 2.

So after:

• Bevor die Videokonferenz beginnt,

the main clause starts like this:

• schreibe ich noch schnell in den Gruppenchat

This is called inversion. English often keeps I write, but German changes the order more strictly.

Bevor means before and is used to introduce a clause:

• Bevor die Videokonferenz beginnt ...
• Before the video conference begins ...

Vorher means beforehand / earlier and is usually an adverb, not a conjunction.

Compare:

• Bevor die Videokonferenz beginnt, schreibe ich noch schnell.
• Vorher schreibe ich noch schnell.

So in this sentence, bevor is the correct word because it introduces a full clause with its own verb.

In German, subordinate clauses are normally separated from the main clause with a comma. Since bevor die Videokonferenz beginnt is a subordinate clause, a comma is required before the main clause begins.

So:

• Bevor die Videokonferenz beginnt, schreibe ich ...

That comma is not optional.

Videokonferenz is a feminine noun, so its dictionary form is:

• die Videokonferenz

In this sentence, it is the subject of beginnt, so it stays in the nominative case:

• die Videokonferenz beginnt

If you are learning noun genders, this is a good one to memorize together:

• die Konferenz
• die Videokonferenz

Because the subject is die Videokonferenz, which is third person singular (it). The verb beginnen is therefore conjugated as:

• ich beginne
• du beginnst
• er/sie/es beginnt
• wir beginnen

So:

• die Videokonferenz beginnt

is exactly the same pattern as:

• die Sitzung beginnt
• das Meeting beginnt

Noch schnell is a very common German combination. Here it means something like:

• just quickly
• real quick
• one quick thing before that

The word noch often adds the sense of still / yet / one more thing, and schnell means quickly.

So:

• schreibe ich noch schnell in den Gruppenchat

means something like:

• I’ll just quickly write in the group chat
• I’ll quickly send one more message in the group chat

It sounds very natural and conversational.

German often leaves the object unstated when it is obvious from context. Here, the listener understands that the speaker means something like:

• eine Nachricht
• etwas
• kurz etwas

So schreibe ich noch schnell in den Gruppenchat means:

• I quickly write something in the group chat
• I quickly send a message in the group chat

Just like in English, you do not always have to say exactly what is being written.

This is a very common question. German often uses in + accusative when something is directed into a space, even metaphorically. Here the message is being posted into the group chat, so:

• in den Gruppenchat

is very natural.

You may also hear:

• im Gruppenchat schreiben

which focuses more on being in the chat as a location or medium.

But with schreiben, in den Chat / in den Gruppenchat schreiben is extremely common because the message is thought of as going into the chat.

No. In modern German, schreiben is often used for digital communication too. It can mean:

• to write
• to type
• to send a message

So in a sentence with Gruppenchat, it naturally means something like:

• to post a message
• to type something into the group chat

This is completely normal everyday German.

Yes. You can also say:

• Ich schreibe noch schnell in den Gruppenchat, bevor die Videokonferenz beginnt.

That is equally correct. The difference is mostly about emphasis:

• Bevor die Videokonferenz beginnt, ... puts the time frame first.
• Ich schreibe noch schnell in den Gruppenchat, bevor ... starts with the action.

Both are natural.

Yes, many speakers would also say:

• Bevor die Videokonferenz anfängt, ...

That is natural too. Both beginnen and anfangen can mean to begin / to start.

A small difference:

• beginnen can sound a bit more neutral or slightly more formal
• anfangen is very common in everyday speech

Also notice the subordinate clause word order with anfangen:

• bevor die Videokonferenz anfängt

The whole verb form still goes at the end.

Yes. German often uses the present tense to talk about the near future, especially when the time is already clear from context.

So:

• Bevor die Videokonferenz beginnt, schreibe ich noch schnell in den Gruppenchat.

uses present tense forms, but it can refer to something that is about to happen. This is very normal in German, just as English can say:

• Before the meeting starts, I’m sending a quick message.