Zaświadczenie potwierdza ważność badania technicznego.

Zaświadczenie is the subject: it means the document doing the action.

Potwierdza is the verb, the 3rd person singular present form of potwierdzać: confirms.

Ważność badania technicznego is the object: the thing being confirmed, literally the validity of the technical inspection.

So the structure is basically:

Zaświadczenie + potwierdza + ważność badania technicznego
certificate + confirms + validity of the technical inspection

Because ważność is a feminine noun ending in -ość, and in the singular its nominative and accusative forms are the same.

Here it is the direct object of potwierdza, so it is in the accusative, but it looks identical to the dictionary form:

• nominative: ważność
• accusative: ważność

That is very normal in Polish. Not every noun visibly changes in every case.

Because after ważność Polish normally uses the genitive to show validity of what?

You can think of it as:

• ważność czego? = the validity of what?
• badania technicznego = of the technical inspection

The base form is:

• badanie techniczne = technical inspection

But in the sentence it changes to the genitive singular:

• badania technicznego

Both the noun and adjective change because they must agree with each other.

That is a very good question. In Polish, adjectives often do come before the noun, but some expressions are fixed or semi-fixed terms, especially in official, legal, and technical language.

Badanie techniczne is a standard official term meaning a formal technical inspection.

If you said techniczne badanie, it might still be understandable, but it would sound less like the established official name and more like a technical kind of examination. So in this case, badanie techniczne is the normal phrase to learn.

Zaświadczenie means an official certificate, attestation, or written confirmation issued by some authority or institution.

It is not always exactly the same as English certificate, because Polish has several related words:

• zaświadczenie = an official statement confirming some fact
• certyfikat = often a certificate of compliance, qualification, standard, etc.
• świadectwo = certificate/report/testimony, depending on context

In this sentence, zaświadczenie is the right kind of formal document that confirms something officially.

Potwierdza is the 3rd person singular present tense form of the infinitive potwierdzać.

So:

• potwierdzać = to confirm (imperfective)
• potwierdza = confirms / is confirming

The perfective partner is potwierdzić.

That means:

• potwierdzać focuses on the process, general fact, or repeated action
• potwierdzić focuses on a completed confirmation

In official statements like this, Polish often uses the present tense to state what a document does: The certificate confirms...

Yes, that is grammatically correct.

It means roughly:

The certificate confirms that the technical inspection is valid.

The difference is mostly one of style:

• Zaświadczenie potwierdza ważność badania technicznego = more compact, formal, bureaucratic
• Zaświadczenie potwierdza, że badanie techniczne jest ważne = more explicit and a bit more conversational

Polish official language often prefers the more condensed noun-based style, which is why ważność appears here instead of jest ważne.

Yes. Polish word order is more flexible than English because case endings show the grammatical relationships.

The given order is the most neutral:

Zaświadczenie potwierdza ważność badania technicznego.

You could rearrange it for emphasis, for example:

Ważność badania technicznego potwierdza zaświadczenie.

That would put more focus on ważność badania technicznego.

So the original sentence is the normal neutral version, but other orders are possible in the right context.

Because Polish has no articles.

So zaświadczenie can mean:

• a certificate
• the certificate

and the context tells you which one is meant.

In an official sentence like this, it will usually be understood as a specific certificate already known from the context, so English often translates it with the.

Often they refer to very similar things, especially in the context of vehicles, but they are not always identical in style.

• badanie techniczne is a more official/legal term
• przegląd techniczny is very common in everyday speech

So in casual conversation someone might say przegląd techniczny auta, while an official document may use badanie techniczne.

In this sentence, the official wording fits very well.

Because the adjective has to match the noun it describes.

The noun here is badania, which is the genitive singular of badanie. Since badanie is a neuter noun, its adjective in the genitive singular takes the form technicznego.

So the agreement is:

• nominative: badanie techniczne
• genitive: badania technicznego

This is a very common pattern in Polish: when the noun changes case, the adjective changes too.