Hinter dem Busch, an dem wir gestern vorbeigegangen sind, sieht man eine dicke Wurzel.

Because hinter can take either the dative or the accusative, depending on meaning.

• dative = location, no movement
• accusative = direction, movement toward somewhere

Here, hinter dem Busch means behind the bush as a fixed location, so German uses the dative.

Compare:

• Hinter dem Busch sieht man eine Wurzel. = The root is located behind the bush.
• Er geht hinter den Busch. = He goes behind the bush.

So dem Busch is correct because this sentence describes where something is seen, not movement toward that place.

Because the noun Busch is involved in two different grammatical relationships.

1. hinter dem Busch

   • This is the location phrase in the main clause.
   • hinter takes the dative here.

2. an dem wir gestern vorbeigegangen sind

   • This is a relative clause describing the bush.
   • The verb vorbeigehen is used with an + dative when you say what you pass by.
   • So the relative pronoun has to match that structure: an dem = by which / past which

So both dem forms refer to Busch, but each belongs to a different part of the sentence.

Here an dem is a combination of:

• the preposition an
• the relative pronoun dem

The verb is an etwas/jemandem vorbeigehen, meaning to walk past something/someone.

So if you want to say the bush that we walked past yesterday, German must keep the preposition:

• der Busch
• an dem wir gestern vorbeigegangen sind

Literally, this is something like:

• the bush by which we walked past yesterday

More natural English would be:

• the bush that we walked past yesterday

German often keeps the preposition directly with the relative pronoun, while English often leaves it implied.

Because that part is a relative clause, and in German, verbs in subordinate clauses go to the end.

The relative clause is:

• an dem wir gestern vorbeigegangen sind

Its basic elements are:

• wir = subject
• gestern = time expression
• vorbeigegangen sind = verb phrase

Since it is a subordinate clause introduced by the relative element an dem, the finite verb sind goes to the end.

This is normal German subordinate-clause word order.

Because vorbeigehen forms its perfect tense with sein, not haben.

Many German verbs that describe:

• movement from one place to another, or
• a change of state

use sein in the perfect.

So:

• wir sind vorbeigegangen = we walked past

Compare with a verb that uses haben:

• wir haben den Busch gesehen = we saw the bush

Since vorbeigehen is a movement verb, sein is correct.

Because vorbeigehen is a verb with a separable element-like structure in actual sentence use.

In an infinitive, you see it together:

• vorbeigehen

In a perfect-tense clause, the participle is:

• vorbeigegangen

But German often places other parts of the clause before that participle, especially in subordinate clauses:

• an dem wir gestern vorbeigegangen sind

You can think of vorbeigegangen sind as the full verbal idea have gone past / walked past placed at the end of the subordinate clause.

The important thing is to recognize vorbeigehen as the dictionary form and vorbeigegangen as its past participle.

Because German main clauses follow the verb-second rule.

The sentence begins with a fronted element:

• Hinter dem Busch, an dem wir gestern vorbeigegangen sind,

That whole location phrase plus relative clause takes the first position. In a German main clause, the finite verb must then come in the second position:

• sieht

After that comes the subject:

• man

So:

• Hinter dem Busch ... sieht man eine dicke Wurzel.

If there were no fronted phrase, you could say:

• Man sieht hinter dem Busch eine dicke Wurzel.

Both are grammatical, but the original puts emphasis first on where the root can be seen.

No. German man here means one, you, people, or someone in a general sense.

So:

• sieht man = you can see, one can see, people can see

It does not mean a man.

This is a very common source of confusion for English speakers because German man looks exactly like the English word man, but it functions differently.

Because it is the direct object of sehen.

The verb sehen takes an accusative object, so:

• eine Wurzel = a root
• eine dicke Wurzel = a thick root

Here:

• eine is the feminine accusative singular article
• dicke is the adjective ending that matches it
• Wurzel is a feminine noun

So the phrase is in the expected accusative form after sehen.

Because it is a relative clause, and German requires commas around relative clauses.

So the structure is:

• main clause element: Hinter dem Busch
• relative clause describing Busch: an dem wir gestern vorbeigegangen sind
• main clause continues: sieht man eine dicke Wurzel

That is why you get:

• Hinter dem Busch, an dem wir gestern vorbeigegangen sind, sieht man eine dicke Wurzel.

In German, these commas are not optional.

In some everyday contexts, learners may hear wo used informally with places, but in this sentence an dem is the standard and grammatically precise choice.

That is because vorbeigehen normally connects with an + dative when you say what you pass by:

• an dem Busch vorbeigehen

So in a relative clause, standard German keeps that preposition:

• der Busch, an dem wir vorbeigegangen sind

Using wo would sound more colloquial and less exact here. For learners, an dem is the form to learn and use.

Yes, two things stand out:

1. German likes to keep the preposition in the relative clause

   • English often says: the bush that we walked past
   • German says: der Busch, an dem wir vorbeigegangen sind

2. German often puts location first for emphasis

   • Hinter dem Busch ... sieht man ...
   • This makes the sentence feel very natural, especially in description or narration.

So even if the sentence feels a bit more structured than English, it is perfectly normal German.