У цієї квартири є балкон, з якого видно парк.

Both are correct.

• У цієї квартири є балкон uses the very common Ukrainian possession pattern у + genitive + є.
  • Literal idea: At this apartment there is a balcony
  • Natural English translation: This apartment has a balcony
• Ця квартира має балкон uses the verb мати = to have.

Ukrainian often prefers the у ... є ... pattern, especially in everyday speech. With things like apartment descriptions, both versions are normal.

It is genitive singular.

Here is why:

• квартира is a feminine singular noun.
• In the possession pattern у + possessor + є + thing possessed, the possessor goes in the genitive.
• So:
  • ця becomes цієї
  • квартира becomes квартири

So у цієї квартири means something like of this apartment / this apartment has.

This is an important distinction.

• у цієї квартири = this apartment has
  • possessive meaning
  • цієї квартири is genitive
• у цій квартирі = in this apartment
  • location meaning
  • цій квартирі is locative

So:

• У цієї квартири є балкон = This apartment has a balcony
• У цій квартирі є балкон = There is a balcony in this apartment

The second one is understandable, but the first one is the clearer way to express possession.

Here є means there is / exists.

In the pattern у X є Y, it is the key word that shows existence or possession:

• У мене є машина = I have a car
• У цієї квартири є балкон = This apartment has a balcony

As a learner, it is best to keep є.

Sometimes Ukrainian omits є in other kinds of present-tense sentences, but in this possession pattern є is very common and natural. Leaving it out here would sound less neutral and more elliptical.

З якого means from which.

It refers back to балкон.

• балкон is masculine singular
• the basic relative pronoun is який = which
• after the preposition з = from, it has to change case
• so який becomes якого

So:

• балкон, з якого видно парк
• literally: a balcony, from which the park is visible
• natural English: a balcony from which you can see the park

Because з якого видно парк is a relative clause describing балкон.

In Ukrainian, relative clauses are normally separated by commas:

• балкон, з якого видно парк
• будинок, який стоїть на розі
• людина, яку я знаю

So the comma works much like English punctuation in non-short relative structures.

Видно is a very common impersonal word in Ukrainian. It means:

• it is visible
• one can see
• you can see

So:

• з якого видно парк
• literally: from which the park is visible
• natural English: from which you can see the park

This is a very natural Ukrainian way to talk about visibility, especially in descriptions of views, windows, balconies, hills, roads, and so on.

It is functioning as the direct object of the idea can see in видно парк.

So it is best understood as accusative singular.

However, because парк is a masculine inanimate noun, its nominative and accusative forms are the same:

• nominative: парк
• accusative: парк

That is why the form does not visibly change.

A clearer example with a feminine noun would be:

• видно вулицю = you can see the street

There, the accusative ending is obvious.

Yes, Ukrainian often alternates з / із / зі for ease of pronunciation.

The meaning stays the same. The choice depends mostly on sound and rhythm.

In this sentence, з якого is completely natural and standard.

You may also meet alternatives in other contexts, for example:

• із школи
• зі столу
• з дому

So this is mainly about euphony, not grammar meaning.

Yes. Some natural alternatives are:

• Ця квартира має балкон, з якого видно парк.
• У цієї квартири є балкон із видом на парк.
• У квартирі є балкон, з якого видно парк.

These are all understandable, but they are slightly different in focus:

• має = directly says has
• із видом на парк = emphasizes the balcony’s view
• у квартирі є балкон = emphasizes the balcony as something present in the apartment

The original sentence is a very natural descriptive sentence.