Der Abnäher verändert die Passform an der Taille.

Abnäher is a sewing/tailoring term. It usually means a dart: a folded and stitched part of a piece of fabric that helps shape a garment so it fits the body better.

So in this sentence, der Abnäher is not a person or an action. It is a specific part of the clothing.

Abnäher is masculine, so its basic article is der.

• der Abnäher = the dart

In this sentence, it is also the subject, so the article stays der:

• Der Abnäher verändert ...

That means the dart changes ...

Because the subject is der Abnäher, which is third person singular.

The verb is verändern = to change / to alter.

Present tense:

• ich verändere
• du veränderst
• er/sie/es verändert
• wir verändern
• ihr verändert
• sie/Sie verändern

Since der Abnäher works like er, the correct form is verändert.

Passform is a feminine noun, so its basic article is die.

• die Passform = the fit

In this sentence, die Passform is the direct object of the verb verändert.
For feminine nouns, the article die stays the same in both nominative and accusative singular.

So:

• nominative: die Passform
• accusative: die Passform

That is why you see die Passform here.

The sentence breaks down like this:

• Der Abnäher = nominative subject
• die Passform = accusative direct object
• an der Taille = prepositional phrase, here with dative

So the structure is:

• Who is doing the action? → der Abnäher
• What is being changed? → die Passform
• Where/in what area? → an der Taille

Because an is a two-way preposition. That means it can take either:

• dative for location
• accusative for direction/movement toward something

Here, the sentence describes location: the fit is being changed at the waist or in the waist area.

So German uses dative:

• an der Taille

If it were about movement toward the waist, you might see an die Taille, but that is not what this sentence means.

It means something like:

• at the waist
• around the waist
• in the waist area

In clothing language, German often uses this kind of phrase to say where on the garment or body the effect is noticeable.

So die Passform an der Taille means the fit at the waist.

Yes. This is a very normal German main-clause word order:

• Der Abnäher = subject
• verändert = finite verb in second position
• die Passform = object
• an der Taille = prepositional phrase

So the pattern is:

Subject + verb + object + extra information

You could also move parts around for emphasis, but this version is the most neutral and straightforward.

Sometimes yes, but verändert is more natural here.

• ändern = to change
• verändern = to alter, modify, change something in its form or condition

In a sewing or fit-related context, verändern often sounds better because it suggests that the dart modifies the fit.

So:

• Der Abnäher verändert die Passform an der Taille.
  sounds very natural in this context.

Because in German, all nouns are capitalized.

In this sentence, the nouns are:

• Abnäher
• Passform
• Taille

The verb verändert is not capitalized because it is a verb, not a noun.

A helpful approximate pronunciation is:

• Abnäher ≈ AHP-nay-er

A few details:

• Ab- sounds like ahp
• nä has an ä sound, roughly like the e in bed, but longer
• -her here is pronounced more like -er in German, not like English hair

Also, the stress is on the first syllable:

• AB-näher

It is singular here:

• die Passform = the fit

The plural is usually:

• die Passformen = the fits / fitting shapes

But in this sentence, singular makes sense because it is talking about the fit of a garment in one area.

Usually, yes, especially in clothing and body-shape contexts.

• die Taille = waist

It is a fairly common word in fashion, tailoring, and descriptions of fit. In everyday conversation, German speakers may also talk about the waist area in other ways, but Taille is very natural in a sentence about garment fit.