Pokuta je vysoká.

Je is the 3rd person singular present form of být (to be).
So Pokuta je vysoká literally means The fine is high.

In Czech, this is the normal way to make a simple present-tense statement with to be:

• Pokuta je vysoká. = The fine is high.
• Dům je velký. = The house is big.

Unlike in some languages, you normally do not leave out je in standard Czech present-tense sentences like this.

Because vysoká has to agree with pokuta.

In Czech, adjectives change their endings to match the noun in:

• gender
• number
• case

Here:

• pokuta is feminine
• singular
• nominative

So the adjective also takes the feminine singular nominative form:

• vysoký = masculine basic dictionary form
• vysoká = feminine singular nominative
• vysoké = neuter singular nominative / some plural uses

That is why you get Pokuta je vysoká, not Pokuta je vysoký.

A good clue is the ending -a. Many Czech nouns ending in -a are feminine.

So:

• pokuta = feminine noun

Because it is feminine, any adjective describing it must use a feminine form:

• vysoká pokuta = a high fine
• Pokuta je vysoká. = The fine is high.

This is not a perfect rule for every noun in Czech, but it works for many common nouns.

Yes, vysoký / vysoká / vysoké often means high or tall, depending on context.

With pokuta (fine), Czech uses high, just like English:

• vysoká pokuta = a high fine

So here it does not mean physically tall. It means that the amount of the fine is large.

This kind of metaphor is very common in both languages.

Not as a complete sentence with the same meaning.

• Vysoká pokuta is just a noun phrase: a high fine / high fine
• Pokuta je vysoká. is a full sentence: The fine is high

So if you want to say something complete, you need je:

• Pokuta je vysoká.

If you only want a phrase, for example as a heading or label, then:

• vysoká pokuta

Czech word order is more flexible than English, but the neutral, most natural order here is:

• Pokuta je vysoká.

You can change the order for emphasis, but it changes the feel:

• Vysoká je pokuta. = marked, poetic, contrastive, or unusual in normal speech
• Je vysoká pokuta. = possible in special contexts, but not the basic neutral sentence

For learners, the best default is:

• subject + je + adjective
• Pokuta je vysoká.

Czech does not have articles like English a/an and the.

So:

• pokuta can mean a fine or the fine
• the exact meaning depends on context

That means:

• Pokuta je vysoká. could be understood as The fine is high or A fine is high, though in normal translation The fine is high is usually the most natural.

Czech relies on context instead of articles.

It is in the nominative case because it is the subject of the sentence.

In:

• Pokuta je vysoká.

the subject is pokuta, so it stands in the nominative.

The adjective vysoká also matches that nominative form because it describes the subject.

So both words are in:

• feminine singular nominative

A simple learner-friendly pronunciation guide is:

• pokuta ≈ POH-koo-tah
• je ≈ yeh
• vysoká ≈ VIH-soh-kah

A few useful notes:

• j in Czech is pronounced like English y
• u is like oo
• á is a long a sound, held a bit longer than short a

So the whole sentence is approximately:

• POH-koo-tah yeh VIH-soh-kah

Stress in Czech normally falls on the first syllable of each word:

• POkuta
• je
• VYsoká

Sometimes yes, but it depends on context.

Czech often drops things that are already clear from the situation. So if everyone already knows you are talking about the fine, then:

• Je vysoká. = It is high.

But out of context, this is less clear, because vysoká is feminine and could refer to any feminine noun. If you want a clear standalone sentence, use:

• Pokuta je vysoká.

The dictionary form is usually given as the masculine singular nominative:

• vysoký

From that base form, you get other endings:

• vysoký = masculine
• vysoká = feminine
• vysoké = neuter

So if you look the word up in a dictionary, you will usually search for vysoký, even though the sentence uses vysoká.