Suma ubezpieczenia jest wysoka.

Because ubezpieczenia is in the genitive singular. After a noun like suma (sum, amount), Polish often uses another noun in the genitive to mean of ....

So:

• suma = sum / amount
• ubezpieczenia = of insurance

Literally, the phrase is structured like sum of insurance.

This is very common in Polish:

• numer telefonu = phone number literally number of phone
• koniec dnia = end of the day
• cena biletu = ticket price

Suma is in the nominative singular.

It is the subject of the sentence:

• Suma ubezpieczenia = the subject
• jest = is
• wysoka = describes the subject

You can think of the basic structure as:

[subject] + [is] + [adjective]

So suma stays in the nominative because it is the thing being talked about.

Because it agrees with suma, and suma is a feminine noun.

In Polish, adjectives must agree with the noun they describe in:

• gender
• number
• case

Here:

• suma = feminine singular nominative
• so the adjective must also be feminine singular nominative
• therefore: wysoka

Compare:

• Dom jest wysoki. = The house is tall/high.
  (dom is masculine)
• Ubezpieczenie jest wysokie. = The insurance is high.
  (ubezpieczenie is neuter)
• Suma ubezpieczenia jest wysoka.
  (suma is feminine)

Jest is the 3rd person singular form of być (to be), so it means is.

The sentence pattern is:

• Suma ubezpieczenia = subject
• jest = is
• wysoka = high

So it works just like English is.

In the present tense, Polish sometimes omits jest in informal speech, especially in very short statements, but in a standard full sentence like this, jest is perfectly normal and natural.

You might hear that in notes, headlines, or very informal spoken language, but for normal standard Polish, Suma ubezpieczenia jest wysoka is the better full sentence.

So:

• Suma ubezpieczenia jest wysoka. = standard, complete
• Suma ubezpieczenia wysoka. = more elliptical, less standard in ordinary writing

For learners, it is safest to keep jest here.

Because Polish does not have articles like English a or the.

So Suma ubezpieczenia jest wysoka can mean:

• The insured amount is high
• The amount of insurance is high
• sometimes simply Insurance coverage is high, depending on context

Polish relies on context instead of articles.

Yes, it is a common insurance-related phrase.

In insurance language, suma ubezpieczenia usually refers to the insured amount, coverage amount, or maximum amount for which something is insured.

So even though the grammar is just ordinary Polish grammar, the whole phrase is also a standard term in the insurance field.

Yes. Polish word order is more flexible than English.

The neutral order here is:

• Suma ubezpieczenia jest wysoka.

But other orders are possible for emphasis, for example:

• Wysoka jest suma ubezpieczenia.
• Jest wysoka suma ubezpieczenia. — less neutral, more marked

The original version is the most natural and neutral for a learner to use.

A rough pronunciation guide is:

u-bez-pye-CHEN-ya

A bit more carefully:

• u like oo
• bez like bez with a short e
• pie here sounds roughly like pye
• cz sounds like English ch
• nia sounds like nya

So the stress is on the second-to-last syllable:

u-bez-pie-CZE-nia

Polish stress is usually on the penultimate syllable, and that is true here as well.

In Polish, wysoki / wysoka / wysokie can mean high or tall, depending on context.

With a physical object like a building:

• wysoki budynek = a tall/high building

With an amount, level, price, salary, or insured sum:

• wysoka cena = high price
• wysoka pensja = high salary
• wysoka suma ubezpieczenia = high insured amount

So here high is the natural English translation.

If you wanted to say The insurance sums are high or The insured amounts are high, you would make both the noun and adjective plural:

• Sumy ubezpieczenia są wysokie.

Changes:

• suma → sumy = plural
• jest → są = are
• wysoka → wysokie = plural adjective form

Notice that ubezpieczenia stays the same in form here, because in this phrase it is still the genitive singular of ubezpieczenie.

Here it is singular, not plural.

That can be confusing, because the ending -a is not always obvious to English speakers.

The base noun is:

• ubezpieczenie = insurance / insurance policy

Its genitive singular form is:

• ubezpieczenia

So in this sentence, it means of insurance, not insurances.

A good first clue is the ending:

• nouns ending in -a are often feminine

So suma is feminine, and that is why you get:

• wysoka, not wysoki or wysokie

Of course, there are exceptions in Polish, but for suma, the rule works normally.

Yes. Once you know the pattern, you can swap in other feminine singular adjectives:

• Suma ubezpieczenia jest niska. = The insured amount is low.
• Suma ubezpieczenia jest duża. = The insured amount is large.
• Suma ubezpieczenia jest maksymalna. = The insured amount is maximum.

The adjective has to stay in the feminine singular form because it still agrees with suma.