Bitte klapp nach der Videokonferenz den Laptop zu, sonst bleibt der Akku nicht lange voll.

This is the informal singular imperative: a command to one person you would call du.

With most verbs, German forms this command by:

• dropping du
• often dropping the ending

So:

• du klappst = you close/fold shut
• klapp! = close!/fold shut!

The longer form klappe! also exists, but klapp! sounds very natural and common in everyday German.

Bitte makes the command more polite: Please close ...

Because the full verb is zuklappen, which is a separable verb.

Its parts are:

• klappen = to fold
• zu = shut/closed

In a main clause or imperative, the prefix separates and goes to the end:

• Ich klappe den Laptop zu.
• Klapp den Laptop zu.

So in your sentence, zu is at the end because it belongs to klapp.

Zuklappen means to fold shut or to close, especially for things with a lid or hinged form, such as:

• a laptop
• a notebook
• a box
• a phone with a flip design

So den Laptop zuklappen is specifically to close the laptop lid.

It is a bit more specific than a general verb like zumachen.

Because nach takes the dative case when it means after in a time expression.

• nominative: die Videokonferenz
• dative: der Videokonferenz

So:

• nach der Videokonferenz = after the video conference

Also, Videokonferenz is a feminine noun, which is why the dative article is der.

Because den Laptop is the direct object of zuklappen, so it is in the accusative case.

Laptop is usually masculine in German:

• nominative: der Laptop
• accusative: den Laptop

So:

• der Laptop = the laptop
• ich klappe den Laptop zu = I close the laptop

Yes. German word order is somewhat flexible, especially with time expressions and objects.

Your sentence has:

• Bitte klapp nach der Videokonferenz den Laptop zu

But these are also possible:

• Bitte klapp den Laptop nach der Videokonferenz zu.
• Klapp bitte nach der Videokonferenz den Laptop zu.

The version you were given is perfectly natural. Placing nach der Videokonferenz earlier gives the time element a little more prominence.

The key rule is that the separable prefix zu still stays at the end.

Yes. Klapp ... zu is the informal singular command, used with du.

So this sentence is addressed to:

• one person
• in an informal context

If you wanted the formal version, you would say:

• Bitte klappen Sie nach der Videokonferenz den Laptop zu.

If you were speaking to several people informally, you would say:

• Bitte klappt nach der Videokonferenz den Laptop zu.

Because German main clauses follow the verb-second rule.

Sonst means otherwise. When it takes the first position in the clause, the conjugated verb must come next.

So:

• Sonst bleibt der Akku nicht lange voll.

Structure:

• position 1: sonst
• position 2: bleibt
• then the subject: der Akku

This is a very common German pattern:

• Dann gehe ich.
• Heute habe ich Zeit.
• Sonst bleibt der Akku nicht lange voll.

German often uses bleiben + adjective to mean stay/remain + adjective.

So:

• voll bleiben = stay full
• ruhig bleiben = stay calm
• offen bleiben = remain open

Here:

• der Akku bleibt voll = the battery stays full / remains fully charged

In context, voll refers to the battery being fully charged, not physically full of something.

Here, nicht is basically negating the idea of for a long time.

So:

• Der Akku bleibt lange voll. = The battery stays full for a long time.
• Der Akku bleibt nicht lange voll. = The battery does not stay full for long.

The meaning is not that the battery is not full. The meaning is that the battery won’t remain full for very long.

That is why the English translation is usually something like:

• otherwise the battery won’t stay charged for long