Částka je správná, položka je však chybná.

Because Czech adjectives must agree with the noun they describe in gender, number, and case.

Here:

• částka = a feminine singular noun
• položka = also a feminine singular noun

So the adjectives must also be feminine singular nominative:

• správná for částka
• chybná for položka

Compare:

• správný = masculine
• správná = feminine
• správné = neuter

Even though the adjectives come after je, they still agree with the subject.

They are in the nominative singular, because they are the subjects of the two clauses:

• Částka je správná
• položka je však chybná

After the verb být (to be), the adjective also stays in the nominative:

• částka je správná
• položka je chybná

So this is a very basic subject + je + adjective structure.

Však adds contrast. In this sentence it means something like however, though, or but.

So the logic is:

• The amount is correct
• the item, however, is incorrect

It signals that the second clause contrasts with the first one.

A very natural English equivalent would be:

• The amount is correct, but the item is incorrect
• or The amount is correct; however, the item is incorrect

Both can express contrast, but they are not used in exactly the same way.

• ale = the most common plain but
• však = often a bit more formal, written, or stylistically polished; often closer to however / though

So:

• Částka je správná, ale položka je chybná.
  = very straightforward, very common

• Částka je správná, položka je však chybná.
  = slightly more formal or elegant

Both are correct. A learner will probably hear ale more often in everyday speech.

Czech word order is relatively flexible, and však often appears early in the clause, but not always in exactly the same spot.

In this sentence:

• položka je však chybná

this placement is natural and idiomatic.

You may also encounter other placements in real Czech depending on style and emphasis, but for learners it is best to treat je však as a normal pattern in sentences like this.

The main thing to remember is:

• však usually does not behave exactly like English however
• you should not try to translate its position word-for-word from English

So learn the whole chunk:

• je však

as a common way to express is, however, ...

Because the sentence contains two main clauses:

1. Částka je správná
2. položka je však chybná

Czech normally separates such clauses with a comma, especially when there is a contrast between them.

So the comma marks the division between:

• first statement
• contrasting second statement

This is similar to English punctuation in a sentence like:

• The amount is correct, but the item is incorrect.

Yes, absolutely.

That version is probably the more obvious one for a learner, and it is very natural Czech.

The difference is mainly stylistic:

• ale = more everyday, direct
• však = a bit more formal or literary in feel

So both are correct:

• Částka je správná, ale položka je chybná.
• Částka je správná, položka je však chybná.

If you are unsure, ale is often the safer choice in conversation.

Because chybný means incorrect, erroneous, containing an error, which fits very well in technical, administrative, or formal contexts.

By contrast, špatný / špatná is broader and can mean:

• bad
• poor
• wrong
• unsuitable

So here:

• chybná položka sounds more precise: the item is incorrect / entered wrongly / in error
• špatná položka could sound more general: the item is bad or wrong in a less exact way

In documents, accounting, forms, and similar contexts, chybný is often the better word.

No. Czech has no articles like a, an, or the.

So:

• částka can mean an amount, the amount
• položka can mean an item, the item, a line item

The exact meaning depends on context.

That is why a single Czech sentence can be translated into English in more than one natural way, depending on what the situation is.

A few useful points:

• Czech stress is normally on the first syllable of the word.
• č sounds like ch in church
• ž sounds like the s in measure
• ch is one sound, like Scottish loch or German Bach, not English ch

Rough pronunciation help:

• Částka ≈ CHAAS-tka
• správná ≈ SPRAAV-naa
• položka ≈ PO-lozh-ka
• však ≈ vshak
• chybná ≈ KHIB-naa or KHYB-naa depending on how you approximate ch

Also remember that á is a long vowel, so:

• správná
• chybná

both have a long final -á sound.