Já sedím na lavičce a dívám se, jak moje děti běží k houpačce.

Yes, já is often optional in Czech because the verb ending already shows who the subject is.

• sedím already means I am sitting
• so Sedím na lavičce... is a complete sentence by itself

Adding já usually gives one of these effects:

• emphasis: I am sitting...
• contrast: I am sitting, while someone else is doing something different
• a slightly more explicit or natural spoken rhythm in some contexts

So this sentence could also be:

• Sedím na lavičce a dívám se, jak moje děti běží k houpačce.

That would sound perfectly normal too.

Sedím is the 1st person singular present tense of sedět (to sit).

So:

• sedět = to sit
• sedím = I sit / I am sitting

In Czech, the present tense often covers both simple and continuous meanings that English separates:

• sedím = I sit or I am sitting, depending on context

Here it clearly means I am sitting.

Because the preposition na requires a specific case here.

In this sentence, na lavičce means on the bench, describing a location. With na used for location, Czech uses the locative case.

• dictionary form: lavička = bench
• locative singular: lavičce
• na lavičce = on the bench

So the pattern is:

• na + locative = location on/on top of/at
• na + accusative = movement onto something

Compare:

• Sedím na lavičce. = I am sitting on the bench.
• Sedám si na lavičku. = I am sitting down onto the bench.

Dívat se is a reflexive verb meaning to look or to watch.

So:

• dívat by itself is not the normal standalone verb for this meaning
• the full verb is dívat se

That means you should learn it as one unit:

• dívat se = to look / to watch
• dívám se = I am looking / I am watching

The se here is not usually translated literally into English. It is just part of the verb.

This is very common in Czech. Many verbs include se as a fixed part of their meaning.

Because se is a clitic, a short unstressed word that tends to go in a fixed position in the sentence.

In simple terms, se usually appears near the beginning of its clause, often in the second position.

So:

• Já se dívám...
• Já dívám se...

The first one is the normal pattern in many contexts, but in this sentence dívám se also works naturally because the clause is structured as:

• Já sedím na lavičce a dívám se...

Learners should mainly remember this:

• se is unstressed
• it does not usually get strong emphasis
• its position is governed by Czech word-order rules, not by English logic

These verbs can overlap, but they are not identical.

• dívat se = to look, to watch
  Neutral and very common.
• koukat se = to look, to watch
  More colloquial; often used in speech.
• sledovat = to observe, to follow, to watch attentively
  Often suggests following something more deliberately.

In this sentence, dívám se is very natural because the speaker is visually watching what the children are doing.

You could also hear:

• koukám se, jak moje děti běží...
  but this is more colloquial

And:

• sleduji svoje děti, jak běží...
  sounds a bit more deliberate or observant

Because jak moje děti běží k houpačce is a subordinate clause.

Czech punctuation normally separates a main clause from a subordinate clause with a comma.

Main clause:

• Já sedím na lavičce a dívám se

Subordinate clause:

• jak moje děti běží k houpačce

So the comma is required.

This is one place where Czech often uses commas more systematically than English learners may expect.

Here jak does not have to be translated as a literal English how.

After verbs of seeing, watching, hearing, and noticing, jak often introduces what someone sees happening. In English, this is often translated more naturally as:

• how
• as
• or sometimes just omitted in a smoother translation

So:

• dívám se, jak moje děti běží...

can mean something like:

• I watch as my children run...
• I watch my children running...

This use of jak is very common after perception verbs.

Both are correct.

• moje děti = my children
• mé děti = my children

The difference is mostly one of style and register:

• moje is very common in everyday speech
• mé is shorter and can sound a bit more formal, literary, or stylistically compact

In normal conversation, moje děti is extremely natural.

Because děti is an irregular plural of dítě (child).

• singular: dítě = child
• plural: děti = children

So it works much like English child → children, not like a regular plural such as book → books.

This is just a form you need to memorize.

Yes, and this is a very common point of confusion.

The verb běží can mean:

• he/she/it runs
• they run

That happens because, in the present tense of some Czech verbs, the 3rd person singular and 3rd person plural have the same form.

So:

• dítě běží = the child runs
• děti běží = the children run

You know whether it is singular or plural from the subject:

• dítě = singular
• děti = plural

Běžet means to run in a neutral sense.

• běží = are running

A verb like utíkat often suggests:

• running away
• hurrying off
• escaping
• or repeated/ongoing running in a slightly different way depending on context

So if the idea is simply that the children are running toward the swing, běží is the most straightforward choice.

Also, Czech aspect matters:

• běžet is imperfective
• that makes sense here because the action is being viewed as in progress

The speaker is watching the children while they are running.

Because k and na express slightly different ideas.

• k houpačce = toward / to the swing
• na houpačku = onto the swing, to get on the swing

In this sentence, the children are running to the swing, not necessarily already climbing onto it. So k houpačce is the natural choice.

Also, k takes the dative case:

• dictionary form: houpačka
• dative singular: houpačce
• k houpačce = to/toward the swing

So the sentence focuses on the direction of movement toward the object, not onto it.

Because the preposition k requires the dative case.

So:

• houpačka = swing
• dative singular: houpačce
• k houpačce = to/toward the swing

This change is part of Czech noun declension.

A useful thing to remember is:

• k + dative

So whenever you see k, expect the following noun to change form.

Czech word order is much more flexible than English word order, but that does not mean it is random.

This sentence is a natural neutral version:

• Já sedím na lavičce a dívám se, jak moje děti běží k houpačce.

You could rearrange parts for emphasis, for example:

• Na lavičce sedím a dívám se, jak moje děti běží k houpačce.
• Jak moje děti běží k houpačce, dívám se z lavičky.

But each version changes the focus, style, or naturalness.

For learners, the safest approach is:

1. learn a neutral word order first
2. notice that Czech uses movement in word order to show emphasis and information structure
3. avoid moving small words like se randomly

Because Czech has no articles.

English needs words like:

• a
• an
• the

Czech usually does not use separate words for this. The meaning comes from context.

So:

• na lavičce can mean on a bench or on the bench
• k houpačce can mean to a swing or to the swing

In this sentence, context makes it clear what is meant.

That is one of the big structural differences between English and Czech.