Learn Hardcore German: Im Büro werden Kundendaten sorgfältig geprüft. - In the office, customer data are checked carefully.

So Im Büro simply means In the office in a more natural, standard form. Using in dem Büro here would sound overly formal or stressed unless you have a specific contrast (e.g. Nicht zu Hause, sondern *in dem Büro nebenan*).

Why is Büro in the dative case after in?

The preposition in can take either dative or accusative:

Dative: location (where something is)
Accusative: direction (where something is going)

Here we are talking about a location:

Im Büro = in the office (where the data are checked)

So Büro is in the dative case:

Nominative: das Büro
Dative: dem Büro → with in → in dem Büro → im Büro

What grammatical structure is werden ... geprüft? Is this passive?

Yes. werden geprüft is the present passive in German.

Pattern:

Form of werden (present)
- past participle
werden … geprüft

So:

Kundendaten werden geprüft. = Customer data are being checked / are checked.

This structure focuses on the action and the object (Kundendaten), not on who does the checking.

Why is the verb werden in second position and geprüft at the end?

German main clauses follow a verb-second rule:

One element in the first position (here: Im Büro)
The conjugated verb in second position (here: werden)
The rest of the sentence, with non-finite verbs (like participles) at the end (here: geprüft)

So the structure is:

Im Büro (first position)
werden (conjugated verb, second position)
Kundendaten sorgfältig geprüft (remainder, with geprüft at the end)

That’s why geprüft goes to the very end.

What tense is werden geprüft? Does it mean “are checked” or “are being checked”?

Werden geprüft is the present tense passive.

In English, this can correspond to:

are checked (general/habitual)
are being checked (right now / ongoing)

German present tense is flexible about aspect. Context decides whether the focus is general or ongoing. This sentence could mean:

In the office, customer data are (generally) carefully checked.
or
In the office, customer data are (currently) being carefully checked.

Who is doing the checking? How would you say that in German?

In passive sentences, the agent (the doer) is often left out because it’s not important, unknown, or obvious from context.

To specify who is doing the checking, you usually add von + dative:

Im Büro werden Kundendaten sorgfältig von den Mitarbeitern geprüft.
= In the office, customer data are carefully checked by the employees.

So:

von
- den Mitarbeitern (dative plural) indicates the agent in the passive.

Why is there no article before Kundendaten? Why not die Kundendaten?

Here, Kundendaten is used in a general or unspecified sense: customer data in general, not some very specific set.

In German, plural nouns can be used:

with article when specific:
- Die Kundendaten werden geprüft. = The (specific) customer data are being checked.
without article when speaking generally or indefinitely:
- Kundendaten werden geprüft. = Customer data (in general) are checked.

So dropping die makes it more like a generic statement about what happens in the office.

What exactly is Kundendaten? Is it one word or two, and why is it plural?

Kundendaten is one compound noun:

der Kunde = customer
die Daten = data
→ die Kundendaten = customer data

A few points:

German very often forms compounds: two nouns joined into one (written together).
Daten in the IT / information sense is typically treated as a plural noun in German (like “data” in careful English).
There is a singular das Datum, but that usually means a calendar date, not “a data item”.

So Kundendaten is naturally plural: (die) Kundendaten.

What is sorgfältig here – an adjective or an adverb? Why doesn’t it change its form?

In this sentence, sorgfältig functions as an adverb describing how the data are checked: carefully.

In German:

Many adverbs are identical in form to adjectives.
They do not get endings when they modify a verb.

Compare:

Er ist sorgfältig. – He is careful. (adjective, predicate)
Er prüft die Daten sorgfältig. – He checks the data carefully. (adverb)

So sorgfältig stays in its base form; it does not change for case, gender, or number when used adverbially.

Could the word order be Kundendaten werden im Büro sorgfältig geprüft? Is that correct?

Yes, that is also correct:

Kundendaten werden im Büro sorgfältig geprüft.

Both versions are grammatical:

Im Büro werden Kundendaten sorgfältig geprüft.
Kundendaten werden im Büro sorgfältig geprüft.

The difference is emphasis:

Starting with Im Büro emphasizes the place: it’s in the office that this happens.
Starting with Kundendaten emphasizes the topic/subject (customer data).

German word order after the finite verb is relatively flexible and often used to adjust focus and emphasis.

Why use the passive here instead of an active sentence like Im Büro prüft man Kundendaten sorgfältig?

Both are possible, but they have different nuances:

Passive:
- Im Büro werden Kundendaten sorgfältig geprüft.
- Focus on the action and the data; the doer is backgrounded or unknown.
Active with “man”:
- Im Büro prüft man Kundendaten sorgfältig.
- More like “In the office, people carefully check customer data.”
- This highlights that some (unspecified) people do the checking.

Passive is especially common in:

Formal language
Technical / process descriptions
When the agent is obvious, unimportant, or intentionally omitted

Is there any difference between geprüft and überprüft in this kind of sentence?

Both are related but not identical:

prüfen = to check, inspect, test, examine
überprüfen = to double-check, verify, review, re-examine (often more thorough or systematic)

So:

Im Büro werden Kundendaten sorgfältig geprüft.
= They are checked / examined carefully.
Im Büro werden Kundendaten sorgfältig überprüft.
= They are checked/verified/reviewed carefully, often implying confirming correctness or re-checking.

In everyday use, there is overlap, but überprüfen often sounds a bit more formal or thorough.

Why is Büro capitalized? And why are Im and werden not?

German capitalization rules:

Nouns are capitalized:
- Büro, Kundendaten
Verbs, adverbs, adjectives (unless nominalized) are not capitalized:
- werden, geprüft, sorgfältig

At the beginning of the sentence, the first word is capitalized regardless of its type:

Here, Im is capitalized because it’s the first word, even though normally im (as a preposition + article) would be lowercase in the middle of a sentence.