Am Zoll öffne ich meinen Koffer.

German often puts the time, place, or other important context first. Here, Am Zoll is placed in the first position to emphasize where the action happens.

But in a normal main clause, the conjugated verb must still be in the second position, so you get:

Am Zoll | öffne | ich | meinen Koffer

This is why ich comes after the verb here. If you started with ich, the sentence would also be correct:

Ich öffne am Zoll meinen Koffer.

Both are grammatical, but the original version gives more focus to the location.

Am is a contraction of an dem.

So:

• an dem Zoll → am Zoll

In this sentence, am Zoll means something like at customs or at the customs checkpoint/desk.

This kind of contraction is very common in German, just like:

• im = in dem
• vom = von dem
• zum = zu dem

German uses different prepositions depending on how a place is understood.

Here, Zoll means customs as an official checkpoint or station, and German idiomatically says am Zoll for at customs.

Using im Zoll would sound unusual, because that would suggest being inside something called the customs in a more literal physical sense. In normal usage, am Zoll is the standard expression.

So this is something you should mostly learn as a set phrase:

• am Zoll = at customs

It is in the dative case.

Since am = an dem, and dem is dative masculine/neuter singular, Zoll here is dative:

• der Zoll → dem Zoll
• an dem Zoll → am Zoll

So am Zoll is a dative phrase.

Because Koffer is the direct object of öffnen, and direct objects take the accusative case.

The noun Koffer is masculine:

• nominative: mein Koffer
• accusative: meinen Koffer

Since I am doing the action and the suitcase is what gets opened, German uses the accusative:

• Ich öffne meinen Koffer.

That is why the ending changes from mein to meinen.

You learn it from the dictionary form:

• der Koffer = the suitcase

Because it is der Koffer, it is masculine. That matters because the article and possessive forms change by case:

• nominative: mein Koffer
• accusative: meinen Koffer
• dative: meinem Koffer

This is one reason it is important to learn German nouns together with their article.

In this sentence, Zoll means customs, as in border control where luggage may be checked.

Be careful, because Zoll can also mean inch in other contexts.

So the word has different meanings depending on context:

• der Zoll = customs
• der Zoll = inch

In Am Zoll öffne ich meinen Koffer, the meaning is clearly customs.

Yes.

The infinitive is öffnen = to open.

For ich, the present tense is:

• ich öffne

So the sentence uses the normal present tense form. The full pattern is:

• ich öffne
• du öffnest
• er/sie/es öffnet
• wir öffnen
• ihr öffnet
• sie/Sie öffnen

Yes. German present tense can be used in several ways, depending on context.

So Am Zoll öffne ich meinen Koffer could mean:

• something happening now
• something that happens regularly
• something that will happen in the future, especially if the context makes that clear

For example, if someone is describing their travel routine, the sentence could mean At customs, I open my suitcase as a habitual action. If they are explaining what they will do on a trip, it could also refer to the future.

Because in German, all nouns are capitalized.

Here:

• Zoll is a noun
• Koffer is a noun

So both begin with capital letters. This is a standard rule in German spelling, unlike English, where common nouns are usually not capitalized.

The ö sound does not exist in the same way in standard English, so it can feel tricky at first.

A rough guide:

• ö is a front rounded vowel
• you can try saying something like eh while rounding your lips

So öffne sounds roughly like EUF-nuh, but that is only an approximation.

Also note:

• the ff makes the preceding vowel short
• the final e in öffne is pronounced as a light uh sound, not silent

So it is approximately:

ÖFF-nuh

Yes, absolutely.

That version is also correct:

Ich öffne meinen Koffer am Zoll.

The difference is mainly emphasis and information structure:

• Am Zoll öffne ich meinen Koffer. → emphasis on where
• Ich öffne meinen Koffer am Zoll. → more neutral, starting with I

German word order is flexible, but the verb still stays in the second position in a main clause.