Увечері вона виходить на балкон і дзвонить сестрі.

Увечері means in the evening.

Yes, увечері and ввечері are basically the same in meaning. Ukrainian often switches between у and в for smoother pronunciation. At the start of a sentence, either form can appear depending on style and sound, though увечері is very common.

So:

• Увечері вона виходить...
• Ввечері вона виходить...

Both mean In the evening, she goes out...

Not necessarily. In Ukrainian, the present tense can describe:

• something happening right now
• a habitual or repeated action
• a general fact

In this sentence, виходить is most naturally understood as a habitual action:

• In the evening, she goes out onto the balcony and calls her sister.

So it sounds like something she usually does.

Also, виходить is from the imperfective verb виходити, which fits repeated or ongoing actions well.

Виходить literally means goes out or comes out. It suggests moving from inside to outside, or out from some enclosed space.

So виходить на балкон means:

• she goes out onto the balcony

If you used йде, that would simply mean goes/is going, without the specific idea of going out from inside.

So:

• виходить на балкон = she steps out onto the balcony
• йде на балкон = she goes to the balcony

The first one is more natural if she is inside and then goes out onto it.

Because Ukrainian uses different cases for movement toward a place and location in a place.

Here, на балкон uses на + accusative because there is motion:

• виходить на балкон = goes out onto the balcony

If you were talking about being located there, you would use на балконі with the locative:

• Вона стоїть на балконі = She is standing on the balcony

So the contrast is:

• на балкон = onto the balcony, toward it
• на балконі = on the balcony, at that location

Because the verb дзвонити takes the dative case, not the accusative.

So:

• дзвонити сестрі = to call the sister / call one’s sister

Here сестрі is the dative singular form of сестра.

This is different from English, where call takes a direct object. In Ukrainian, the pattern is closer to ring to someone historically, so the person is in the dative.

Compare:

• Я бачу сестру = I see my sister
  
  • сестру = accusative
• Я дзвоню сестрі = I call my sister
  
  • сестрі = dative

In this sentence, yes, that is the natural meaning.

The verb дзвонити can literally relate to ringing, but when used with a person in the dative, it commonly means to phone/call someone:

• дзвонити мамі
• дзвонити другові
• дзвонити сестрі

So дзвонить сестрі means she calls her sister or she phones her sister.

Yes, вона can be omitted if the subject is already clear from context.

Ukrainian often leaves out subject pronouns because the verb ending already gives information about the person and number. However, in the third person singular, the form виходить could mean he, she, or it, so вона helps make the subject explicit.

So:

• Увечері вона виходить на балкон і дзвонить сестрі = clear: she
• Увечері виходить на балкон і дзвонить сестрі = possible, but only if context already tells us who it is

Ukrainian word order is fairly flexible, but the sentence you have is a very natural neutral order:

• Увечері = time expression first
• вона = subject
• виходить на балкон = first action
• і дзвонить сестрі = second action

This order sounds smooth and straightforward.

You could change the order for emphasis, for example:

• Вона увечері виходить на балкон і дзвонить сестрі
  This emphasizes she
• На балкон вона виходить увечері і дзвонить сестрі
  This gives special focus to onto the balcony

But the original version is the most neutral and likely the best for learners to model.

І means and.

It simply joins the two actions:

• виходить на балкон = goes out onto the balcony
• дзвонить сестрі = calls her sister

So the structure is:

• She goes out onto the balcony and calls her sister

Ukrainian also has й as a variant of і, chosen sometimes for smoother pronunciation, but і is perfectly normal here.

Yes, stress can help with pronunciation. A learner will often hear these stressed like this:

• уве́чері
• вона́
• вихо́дить
• на балко́н
• дзвони́ть
• сестрі́

A few especially useful ones to remember:

• балко́н
• дзвони́ть
• сестрі́

Stress in Ukrainian is not always predictable, so it is worth learning it together with each word.