Bevor die Videokonferenz beginnt, stummschalte ich mein Handy und synchronisiere kurz den Kalender.

Because bevor is a subordinating conjunction. In German, a clause introduced by a subordinating conjunction sends the conjugated verb to the end of that clause.

So:

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

You will see the same pattern with other words like weil, dass, wenn, obwohl, etc.

Examples:

• Weil ich müde bin, gehe ich früh ins Bett.
• Wenn der Film anfängt, bin ich schon da.

German uses a comma to separate a subordinate clause from a main clause.

Here, the first part is the subordinate clause:

• Bevor die Videokonferenz beginnt

And the second part is the main clause:

• stummschalte ich mein Handy und synchronisiere kurz den Kalender

So the comma is required.

This is because of the verb-second rule in German main clauses.

When the sentence starts with the subordinate clause Bevor die Videokonferenz beginnt, that whole clause takes the first position. Then the conjugated verb of the main clause must come immediately after it.

So the structure is:

• [Subordinate clause] + [conjugated verb] + [subject] + ...

That gives:

• Bevor die Videokonferenz beginnt, stummschalte ich mein Handy ...

A very similar pattern:

• Wenn ich nach Hause komme, esse ich zuerst.
• Nach der Arbeit gehe ich einkaufen.

In both cases, the verb comes before the subject in the main clause because something else is in first position.

This is a very useful question, because learners often notice that stummschalten behaves a bit differently from what they expect.

In standard everyday German, the most common main-clause wording is:

• Ich schalte mein Handy stumm.

The infinitive is:

• stummschalten

And the past participle is usually:

• stummgeschaltet

So learners are safest with:

• Bevor die Videokonferenz beginnt, schalte ich mein Handy stumm ...

The one-word finite form stummschalte may be encountered, especially in technical or compact written language, but schalte ... stumm is the most natural pattern to learn first.

Both are possible, but they mean slightly different things.

• mein Handy = my phone
• den Kalender = the calendar

Using den Kalender suggests a specific calendar that is already understood from context, such as:

• your digital calendar
• the office calendar
• the calendar app

If you say meinen Kalender, you are emphasizing that it is your calendar.

So:

• Ich synchronisiere den Kalender. = I sync the calendar.
• Ich synchronisiere meinen Kalender. = I sync my calendar.

The sentence you were given is perfectly normal if the calendar is obvious from the situation.

Because synchronisieren takes a direct object, and the direct object is in the accusative case.

The noun der Kalender is masculine, so its accusative form is:

• der Kalender → den Kalender

Compare:

• Ich sehe den Kalender.
• Ich öffne den Kalender.
• Ich synchronisiere den Kalender.

If it were dative, you would use dem, but that is not what this verb requires here.

Here kurz means briefly, for a moment, or quickly in the sense of just for a short time.

So:

• synchronisiere kurz den Kalender

means something like:

• briefly sync the calendar
• quickly sync the calendar

It does not mean the calendar is short. Here kurz is an adverb describing the action.

You will often hear kurz used like this in everyday German:

• Ich schaue kurz nach. = I’ll check quickly.
• Ich rufe dich kurz an. = I’ll call you briefly.

German often uses the present tense to talk about the future, especially when the future event is scheduled, expected, or clear from context.

So:

• Bevor die Videokonferenz beginnt

means before the video conference starts, even though it is still in the future.

This is very normal in German.

Examples:

• Der Zug fährt um acht ab. = The train leaves at eight.
• Morgen arbeite ich von zu Hause. = Tomorrow I’m working from home.

You could use a future form in some contexts, but the present tense is the usual choice here.

Because the same subject applies to both verbs:

• stummschalte ich mein Handy
• und synchronisiere kurz den Kalender

German often omits the repeated subject after und when it is clearly the same.

So this is completely natural.

You could also say:

• ..., stummschalte ich mein Handy und ich synchronisiere kurz den Kalender.

But that sounds heavier and less natural unless you want emphasis.

Yes. That is very common.

You can say:

• Ich schalte mein Handy stumm und synchronisiere kurz den Kalender, bevor die Videokonferenz beginnt.

When the main clause comes first, normal word order returns:

• Ich
  • verb

So compare:

• Bevor die Videokonferenz beginnt, schalte ich mein Handy stumm.
• Ich schalte mein Handy stumm, bevor die Videokonferenz beginnt.

Both are correct. The difference is mostly about emphasis and flow.

No. This is a classic false friend.

In German, das Handy means:

• mobile phone
• cell phone

But in English, handy usually means:

• useful
• convenient

So:

• Ich nehme mein Handy mit. = I’m taking my phone with me.

Not:

• I’m taking my useful with me.

Because Videokonferenz is a feminine noun.

Its grammatical gender is:

• die Videokonferenz

This is mainly because the base noun Konferenz is feminine:

• die Konferenz

And compounds usually keep the gender of the last part of the word.

Other examples:

• die Telefonkonferenz
• die Pressekonferenz
• die Jahreskonferenz

All are feminine because the final element is Konferenz.

Yes. German very often combines nouns into a single compound word.

So:

• Video
  • Konferenz = Videokonferenz

This is extremely normal in German. English often writes similar ideas as separate words, but German usually joins them.

More examples:

• Handykamera
• Kalender-App
• Bürotür
• Zugticket

A good rule is that the last part tells you the basic meaning and usually the gender.

So Videokonferenz is a kind of Konferenz.