Z tych klocków dzieci budują wieżę, chociaż jeden klocek ciągle spada.

Because z here means from / out of, and in that meaning it requires the genitive case.

• basic form: te klocki = these blocks
• after z: z tych klocków = from these blocks / using these blocks

So:

• te → tych
• klocki → klocków

This is a very common pattern in Polish:

• z domu = from the house
• z książki = from the book
• z tych klocków = from these blocks

In this sentence, z tych klocków means something like using these blocks or out of these blocks.

Klocek means block, especially a toy block or building block.
The plural is klocki.

So:

• jeden klocek = one block
• te klocki = these blocks

In this sentence, it most naturally refers to toy building blocks, not to a brick in a wall.

Dzieci is the irregular plural of dziecko (child).

• singular: dziecko = child
• plural: dzieci = children

Here dzieci is in the nominative plural, because it is the subject of budują:

• dzieci budują = the children are building / children build

This is an important irregular noun, so it is worth memorizing as a whole pair:

• dziecko → dzieci

Budują is the 3rd person plural present tense of budować (to build).

So:

• ja buduję = I build / am building
• ty budujesz = you build
• oni / one budują = they build / are building

Since the subject is dzieci (children), you need the plural form:

• dzieci budują = the children are building

Also, Polish present tense often covers both:

• they build
• they are building

The exact English translation depends on context.

Because wieża (tower) is the direct object of budują, so it goes into the accusative case.

• nominative: wieża = tower
• accusative: wieżę = tower (as the thing being built)

So:

• Wieża jest wysoka. = The tower is tall.
  Here wieża is the subject.
• Dzieci budują wieżę. = The children are building a tower.
  Here wieżę is the object.

This is a very common feminine singular pattern in Polish:

• książka → książkę
• lampa → lampę
• wieża → wieżę

Chociaż means although / even though.

It introduces a subordinate clause:

• chociaż jeden klocek ciągle spada = although one block keeps falling

Polish normally uses a comma before conjunctions introducing this kind of subordinate clause, including chociaż.

So the sentence is divided like this:

• Z tych klocków dzieci budują wieżę,
• chociaż jeden klocek ciągle spada.

This is very similar to English:

• The children are building a tower from these blocks, although one block keeps falling.

Jeden klocek means one block.

Here it is the subject of the second clause, so it stays in the nominative singular:

• jeden = one
• klocek = block

Together:

• jeden klocek ciągle spada = one block keeps falling

Nothing unusual is happening grammatically here; it is just the subject of the verb spada.

Ciągle means constantly, continually, or very often keeps in natural English translation.

So:

• ciągle spada = keeps falling / is constantly falling

In everyday Polish, ciągle is very common and often means repeated or ongoing action.

Examples:

• On ciągle mówi. = He keeps talking.
• Pada ciągle deszcz. = It’s raining constantly.
• Jeden klocek ciągle spada. = One block keeps falling.

Yes, spada is 3rd person singular present tense of the imperfective verb spadać (to fall, in an ongoing or repeated sense).

Because the subject is singular:

• jeden klocek spada = one block falls / is falling

The imperfective verb is used because the action is presented as:

• ongoing,
• repeated,
• habitual.

That fits very well with ciągle:

• ciągle spada = keeps falling

If you used the perfective verb spaść, it would not normally be used for this kind of repeated ongoing idea in the present.

Yes, budują comes from budować, which is imperfective.

Imperfective is used because the action is seen as:

• in progress,
• repeated,
• not presented as completed.

That is exactly right for children who are in the middle of building a tower.

Compare:

• dzieci budują wieżę = the children are building a tower
• dzieci zbudują wieżę = the children will build the tower / will manage to build the tower

The perfective verb zbudować would not normally be used here in the present tense with a present meaning, because perfective present forms usually refer to the future in Polish.

Yes, you could say Dzieci budują wieżę z tych klocków. Polish word order is much more flexible than English.

The original:

• Z tych klocków dzieci budują wieżę...

puts z tych klocków first, which gives it a bit more focus, like:

• From these blocks, the children are building a tower...

A more neutral order is:

• Dzieci budują wieżę z tych klocków.

Both are grammatical. The difference is mainly about focus and emphasis, not basic meaning.

Polish has both z and ze.
Ze is used mainly for easier pronunciation before certain consonant combinations.

Here z tych klocków is easy to pronounce, so z is normal.

You often see ze in phrases like:

• ze szkoły = from school
• ze mną = with me
• ze stołu = from the table

But:

• z domu
• z Polski
• z tych klocków

So in this sentence, z is the expected form.

Literally, it is from these blocks / out of these blocks.
In natural English, depending on context, that often becomes:

• from these blocks
• with these blocks
• using these blocks

Polish often uses z + genitive where English might prefer with.

So all of these can express the idea well:

• The children are building a tower from these blocks.
• The children are building a tower with these blocks.
• The children are building a tower using these blocks.

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

So:

• dzieci can mean children or the children
• wieżę can mean a tower or the tower
• jeden klocek means one block

You understand whether something is definite or indefinite from:

• context,
• word order,
• emphasis,
• or extra words if needed.

So dzieci budują wieżę could be:

• children are building a tower
• the children are building a tower
• sometimes even the children are building the tower, if context makes that clear

Yes. Dzieci is a general plural meaning children, regardless of gender.

It can refer to:

• boys,
• girls,
• or a mixed group.

This is completely normal and does not need any extra marking.

A very natural translation would be:

• The children are building a tower out of these blocks, although one block keeps falling.

Other natural versions are:

• The children are building a tower with these blocks, although one block keeps falling.
• Using these blocks, the children are building a tower, although one block keeps falling.

The most natural choice depends on the context, but out of these blocks or with these blocks is especially idiomatic here.