Ta herbata jest delikatna, a moja żona lubi właśnie takie spokojne wieczory.

Because herbata is a feminine noun in Polish.

The demonstrative this has to agree with the gender of the noun:

• ten = masculine
• ta = feminine
• to = neuter

So:

• ta herbata = this tea
• compare: ten stół = this table
• compare: to okno = this window

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

Here, herbata is:

• feminine
• singular
• nominative (it is the subject)

So the adjective also has to be feminine singular nominative:

• delikatny = basic dictionary form
• delikatna herbata = delicate/mild tea

If the noun were masculine, you would get delikatny, and if it were neuter, delikatne.

In standard Polish, you normally do use jest in sentences like this.

So:

• Ta herbata jest delikatna. = This tea is delicate/mild.

Unlike some languages, Polish usually does not drop the present tense of to be in normal statements.

So Ta herbata delikatna would sound incomplete or unnatural in standard Polish.

A is a very common Polish conjunction that often means something like:

• and
• while
• whereas
• sometimes a mild but

In this sentence, it links two related ideas with a slight contrast or shift of focus:

• Ta herbata jest delikatna, a moja żona lubi właśnie takie spokojne wieczory.

It is not as strong as ale (but).
Here, a feels natural because the speaker moves from one observation to another related one.

So depending on context, it may feel like:

• This tea is mild, and my wife likes exactly such quiet evenings.
• or This tea is mild, while my wife likes exactly such quiet evenings.

Because in Polish, clauses joined by a are normally separated by a comma.

So the punctuation here is standard:

• Ta herbata jest delikatna, a moja żona lubi...

This is one of the basic punctuation rules in Polish.

Because moja żona is the subject of the second clause:

• moja żona lubi... = my wife likes...

Subjects are usually in the nominative case.

So:

• moja żona = nominative
• moją żonę = accusative

You would use moją żonę if she were the object, for example:

• Widzę moją żonę. = I see my wife.

But here she is the one doing the liking, so we need moja żona.

Właśnie is a focus word. Here it adds emphasis and means something like:

• exactly
• just
• precisely

So:

• moja żona lubi właśnie takie spokojne wieczory

means something like:

• my wife likes exactly those kinds of quiet evenings
• my wife likes just that sort of quiet evening

It highlights that this is the kind of evening she especially likes.

This phrase means such quiet evenings or that kind of quiet evenings.

Let’s break it down:

• takie = such / that kind of
• spokojne = quiet / calm / peaceful
• wieczory = evenings

All the words have to match grammatically.

Since wieczory is:

• plural
• masculine inanimate
• here used in the accusative plural after lubić

the adjective and demonstrative take the plural non-masculine-personal form:

• takie spokojne wieczory

This is normal because wieczory refers to things, not people.

After lubić (to like), Polish uses the accusative case.

So the object of lubi must be accusative:

• lubi wieczory

However, for many masculine inanimate plural nouns, the accusative plural looks the same as the nominative plural.

So here:

• nominative plural: wieczory
• accusative plural: wieczory

That is why the form does not change, even though the case has changed.

Because Polish often uses the plural when talking about a type of thing in general.

So:

• lubi takie spokojne wieczory
  means she likes evenings of that kind in general

This sounds natural when speaking about preferences or repeated experiences.

A singular form would change the meaning and sound more like one specific evening or a more abstract phrasing.

Because after lubić, we need the accusative, and with non-masculine-personal plural nouns, the accusative plural adjective looks like the nominative plural adjective.

So:

• spokojne wieczory = accusative plural here

You would get spokojnych in other situations, for example in the genitive:

• Nie ma spokojnych wieczorów. = There are no quiet evenings.

So in this sentence, spokojne is exactly the correct form.

Yes. Polish word order is quite flexible.

The sentence as given is natural and neutral:

• Ta herbata jest delikatna, a moja żona lubi właśnie takie spokojne wieczory.

But you could change the order for emphasis, for example:

• Ta herbata jest delikatna, a właśnie takie spokojne wieczory lubi moja żona.

This puts stronger focus on właśnie takie spokojne wieczory.

So the basic meaning stays similar, but the emphasis changes.

It can mean all of those, depending on context.

Spokojny is a broad adjective that can suggest:

• quiet
• calm
• peaceful
• relaxing

So spokojne wieczory could describe evenings that are not noisy, not stressful, and generally restful.

That is why it is a very natural phrase in Polish.