Wenn du auf den Link klickst, öffnet sich das Dokument sofort.

Wenn can mean if, when, or whenever, depending on context.

In this sentence, it expresses a general condition:

• Wenn du auf den Link klickst, ... = If/When you click the link, ...

In English, both if and when can sound natural here. German often uses wenn for repeated or general situations like this.

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

So:

• du klickst auf den Link = normal main clause order
• wenn du auf den Link klickst = subordinate clause, so klickst moves to the end

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

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

So in:

• Wenn du auf den Link klickst, öffnet sich das Dokument sofort.

the comma marks the end of the wenn-clause and the start of the main clause.

In German, this comma is required.

Because the German verb klicken is commonly used with the preposition auf when you mean to click on something.

So German says:

• auf den Link klicken = to click on the link

This works a lot like English click on.

Because auf here takes the accusative case, and Link is masculine:

• der Link = nominative
• den Link = accusative

Since the expression is auf + accusative here, you get:

• auf den Link

Because the sentence begins with a subordinate clause:

• Wenn du auf den Link klickst, ...

After that, the main clause still follows the verb-second rule. That means the conjugated verb must come first within the main clause, before the subject.

So the main clause is:

• öffnet = first element of the main clause
• sich
• das Dokument = subject
• sofort

That is why you get:

• ..., öffnet sich das Dokument sofort.

If the sentence stood alone, you would normally say:

• Das Dokument öffnet sich sofort.

Both are correct; the word order changes because of what comes first in the full sentence.

Sich is the reflexive pronoun. Here it is part of the expression sich öffnen.

• Das Dokument öffnet sich. = The document opens.

This is a common German way to say that something opens, especially in technical or interface-style language.

Compare:

• Du öffnest das Dokument. = You open the document.
  (someone actively opens it)

• Das Dokument öffnet sich. = The document opens.
  (it opens / it opens itself)

German often uses reflexive verbs where English does not.

Yes. Das Dokument is the subject of the main clause.

A learner might expect the subject to come before the verb, but German does not always work that way. In this sentence, the verb öffnet comes first in the main clause because of the verb-second rule, and the subject follows it:

• öffnet sich das Dokument sofort

So even though das Dokument comes later, it is still the thing that is opening.

Also, das Dokument is in the nominative case, which helps show that it is the subject.

Because Dokument is a neuter noun:

• das Dokument

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

• das Dokument

If it were in another case, the article might change, but for neuter nouns the nominative and accusative singular are both das.

Sofort means immediately. Its position here is very natural and neutral.

• ..., öffnet sich das Dokument sofort.

German adverbs can often move around, but the end position sounds normal and clear in a sentence like this.

You may also see other placements for emphasis, but this version is standard and natural.

Because German often uses the present tense for:

• general truths
• instructions
• habitual actions
• future meaning when the context is clear

So:

• Wenn du auf den Link klickst, öffnet sich das Dokument sofort.

uses present tense even though English might also think of it as a future result. This is completely normal in German.

Yes, it could.

• du is informal singular
• Sie is formal

So a more formal version would be:

• Wenn Sie auf den Link klicken, öffnet sich das Dokument sofort.

Websites, apps, and instructions may use either form depending on tone and audience.

Yes. This kind of sentence is very common in instructions, software text, and help pages.

It sounds natural because it describes a direct result of an action:

• Wenn du X machst, passiert Y.

That pattern is extremely useful in German:

• Wenn du auf Start klickst, beginnt das Programm.
• Wenn du das Passwort eingibst, wird der Zugang aktiviert.

So this sentence is a very practical model to learn from.