Am Check-in-Schalter prüft die Mitarbeiterin meinen Reisepass.

German often puts a time/place expression first when it is the thing the speaker wants to emphasize.

So instead of starting with the subject:

Die Mitarbeiterin prüft meinen Reisepass am Check-in-Schalter.

German can also start with the location:

Am Check-in-Schalter prüft die Mitarbeiterin meinen Reisepass.

Both are correct. The second version highlights where the action happens.

Because German main clauses usually follow the verb-second rule.

That means the finite verb must be in the second position of the clause. If Am Check-in-Schalter comes first, then the verb prüft must come second:

• Am Check-in-Schalter = first position
• prüft = second position
• die Mitarbeiterin = comes after the verb

This is very normal German word order.

Am is a contraction of an dem.

• an = at / on
• dem = the (dative masculine or neuter)

So:

• an dem Check-in-Schalter becomes
• am Check-in-Schalter

Here it means something like at the check-in counter.

German uses different prepositions depending on the natural expression.

With Schalter (counter, desk, booth), German commonly says am Schalter.

So:

• am Check-in-Schalter = at the check-in counter

Using im would mean in the, and that usually does not fit naturally with Schalter.

In German, the subject does not always come first.

Here, die Mitarbeiterin is still the subject because it is in the nominative case and because it is the person performing the action of prüfen.

German word order is more flexible than English word order. Position does not automatically tell you what the subject is.

Because Mitarbeiterin is a feminine noun, and here it is in the nominative singular as the subject.

The nominative singular definite article for feminine nouns is die.

So:

• die Mitarbeiterin = the female employee / staff member

If it were masculine, it would be:

• der Mitarbeiter

Because Reisepass is the direct object of prüft, so it is in the accusative case.

Reisepass is a masculine noun:

• nominative: mein Reisepass
• accusative: meinen Reisepass

So the possessive word mein changes to meinen in the masculine accusative.

You learn it together with its article:

• der Reisepass = passport

Because it is masculine, its forms change like this:

• nominative: der Reisepass
• accusative: den Reisepass

And with mein:

• nominative: mein Reisepass
• accusative: meinen Reisepass

That is why the sentence has meinen Reisepass.

It is a mixed expression that uses an English borrowing plus a German noun.

• Check-in comes from English
• Schalter is German and means counter / desk / booth

This kind of combination is very common in modern German, especially in travel and airport language.

The important part for grammar is that the whole compound behaves like der Schalter, so it is masculine.

Yes. That is also correct.

German allows several word orders, especially when moving place expressions around. These versions are all possible, with slightly different emphasis:

• Die Mitarbeiterin prüft meinen Reisepass am Check-in-Schalter.
• Am Check-in-Schalter prüft die Mitarbeiterin meinen Reisepass.

The meaning is basically the same, but the second version puts more focus on the location.

Because in German, all nouns are capitalized.

So in this sentence you get:

• Check-in-Schalter
• Mitarbeiterin
• Reisepass

This is a standard rule in German spelling, unlike English.

Mitarbeiterin is the feminine form of Mitarbeiter.

• der Mitarbeiter = male employee / staff member
• die Mitarbeiterin = female employee / staff member

The ending -in often makes a noun specifically feminine in German.

Plural:

• die Mitarbeiter = employees (mixed or all male, depending on context)
• die Mitarbeiterinnen = female employees

Prüft comes from the verb prüfen, meaning to check, to examine, or to inspect.

It is the third person singular present tense form:

• ich prüfe
• du prüfst
• er/sie/es prüft

Since die Mitarbeiterin is she, the sentence uses prüft.

A rough guide is:

• am → like ahm
• Check-in → similar to English check in
• Schalter → roughly SHAL-ter

A few useful pronunciation notes:

• sch in German sounds like English sh
• ch in Check here is pronounced like English ch, because it is a borrowing
• er at the end of Schalter is usually a weak -er sound, not a strong English r

So the whole phrase sounds roughly like:

ahm CHECK-in SHAL-ter