Das Lesezeichen, auf das ich gestern geklickt habe, führt direkt zu dem Artikel, den ich brauchte.

It has a main clause with two relative clauses inserted into it:

• Main clause: Das Lesezeichen ... führt direkt zu dem Artikel ...
• Relative clause 1: auf das ich gestern geklickt habe
  • This describes das Lesezeichen
• Relative clause 2: den ich brauchte
  • This describes dem Artikel

So the sentence is built like this:

• The bookmark, [which I clicked on yesterday], leads directly to the article [that I needed].

This kind of nested structure is very common in German.

Because both parts are relative clauses, and in German relative clauses are always separated by commas.

So:

• Das Lesezeichen, auf das ich gestern geklickt habe, ...
• ... zu dem Artikel, den ich brauchte.

Even if the sentence feels short, the commas are required in standard German.

Because the verb expression is auf etwas klicken = to click on something.

The preposition auf belongs to the verb here, so it must stay:

• auf das = on which

If you removed auf, the grammar would change and the sentence would no longer match the verb klicken auf.

Compare:

• Ich klicke auf das Lesezeichen.
• Das Lesezeichen, auf das ich klicke, ...

So the relative clause keeps the same preposition that the verb needs.

Because klicken auf takes the accusative.

So:

• auf das Lesezeichen klicken
• relative version: das Lesezeichen, auf das ich geklickt habe

It is not dative here, so auf dem would be wrong in this sentence.

A helpful way to think of it:

• auf + accusative often appears with actions directed toward something
• auf + dative often appears with location

Here, clicking is directed at the bookmark, so German uses accusative.

Because relative clauses are subordinate clauses, and in German subordinate clauses send the conjugated verb to the end.

Examples from the sentence:

• ..., auf das ich gestern geklickt habe
• ..., den ich brauchte

In the first clause, the full verb form is split:

• habe geklickt
• In a subordinate clause, both parts go to the end, with the participle before the auxiliary:
  • ... geklickt habe

This is one of the most important word-order rules in German.

German is mixing two past forms:

• habe geklickt = Perfekt
• brauchte = Präteritum

This is normal German usage.

Why the difference?

• In everyday spoken German, many actions are commonly expressed with Perfekt, especially verbs like klicken
• Some verbs, especially very common ones, often appear naturally in Präteritum too, and brauchte is perfectly normal

So the sentence is not strange. German often mixes past tenses if it sounds natural in context.

You could also say:

• ..., den ich gebraucht habe.

That is also possible, but den ich brauchte sounds a bit more concise and written-style.

Because the verb is zu etwas führen = to lead to something.

So it needs the preposition zu.

• führen zu + dative
• zu dem Artikel

That is why the sentence says:

• führt direkt zu dem Artikel

not:

• führt den Artikel

The second version would mean something completely different and would not fit here.

Both are correct.

• zu dem Artikel
• zum Artikel

Since zu dem contracts to zum, most speakers would probably say or write:

• führt direkt zum Artikel

The uncontracted form zu dem is still grammatical. It can sound a little more explicit or formal, or it may simply be chosen to keep the structure clearer for learners.

Because den is the relative pronoun referring to Artikel, and inside the relative clause it is the direct object of brauchte.

Ask the question inside the clause:

• Ich brauchte wen oder was?
• den Artikel

That means the relative pronoun must be accusative masculine singular:

• nominative: der
• accusative: den

So:

• der Artikel
• den ich brauchte

This is a very common pattern in German relative clauses: the case depends on the role inside the relative clause, not just on the original noun.

Because the same noun is playing two different grammatical roles.

1. In the main clause:

   • zu dem Artikel
   • The preposition zu requires dative
   • So we get dem Artikel

2. In the relative clause:

   • den ich brauchte
   • Here the article is the direct object of brauchte
   • So we get den

So:

• dem = dative, because of zu
• den = accusative, because it is the object of brauchen

This is a classic thing in German: the noun and the relative pronoun can have different cases.

Yes, that is also possible.

There are two natural ways to express this idea:

• auf das ich gestern geklickt habe
• das ich gestern angeklickt habe

Why?

• auf etwas klicken = to click on something
• etwas anklicken = to click something

So the first version uses a verb with a preposition, and the second uses a direct object.

Both are good German. The original sentence uses klicken auf, which is why the relative clause becomes auf das.

Yes. Lesezeichen is the normal German word for bookmark, including a browser bookmark.

Depending on context, it can mean:

• a physical bookmark in a book
• a saved bookmark in a browser or app

In this sentence, because it says geklickt and führt direkt zu dem Artikel, it clearly means a digital bookmark.

Not in this sentence, if you want standard grammar.

Since the clause refers back to the noun das Lesezeichen, German normally uses:

• das Lesezeichen, auf das ich geklickt habe

Worauf is a pronominal adverb, and it is usually used when there is no noun stated directly before it, for example:

• Worauf hast du geklickt?
• Auf das Lesezeichen.

So after a clear noun antecedent like das Lesezeichen, the standard relative form is auf das, not worauf.

It is nominative, because it is the subject of the main clause.

The main clause is:

• Das Lesezeichen führt direkt zu dem Artikel.

Ask:

• What leads directly to the article?
• Das Lesezeichen

So das Lesezeichen is nominative neuter singular.

Direkt is an adverb meaning directly. It modifies führt.

So:

• führt direkt zu dem Artikel = leads directly to the article

Its placement is normal: it comes in the middle part of the clause, before the prepositional phrase zu dem Artikel.

German adverb placement can vary, but this position is very natural.

It sounds a bit more written or at least carefully structured, mainly because of the two relative clauses:

• Das Lesezeichen, auf das ich gestern geklickt habe, führt direkt zu dem Artikel, den ich brauchte.

In everyday speech, many speakers might simplify it, for example:

• Das Lesezeichen, auf das ich gestern geklickt habe, führt direkt zu dem Artikel, den ich gesucht habe.
• Das Bookmark von gestern führt direkt zu dem Artikel, den ich brauchte.
• Ich habe gestern auf ein Lesezeichen geklickt; das führt direkt zu dem Artikel, den ich brauchte.

But the original sentence is completely natural and grammatically good.