Po kolacji czytam dzieciom krótką bajkę o lesie i małym króliku.

Because the preposition po usually requires the locative case when it means after in expressions of time.

• kolacja = dinner
• po kolacji = after dinner

So kolacji is the locative form of kolacja.

A few similar examples:

• po pracy = after work
• po obiedzie = after lunch
• po szkole = after school

Czytam is the 1st person singular present tense of czytać.

It can mean either:

• I read (habitually / regularly), or
• I am reading (right now)

Polish present tense often covers both meanings, and context tells you which one is intended.

So this sentence could mean:

• After dinner, I read the children a short story...
  or
• After dinner, I am reading the children a short story...

depending on the situation.

Because Polish often shows to whom something is done by using the dative case, not a separate word like English to.

Here:

• dzieciom = to the children

So in:

• czytam dzieciom bajkę

the word dzieciom already includes the idea of to the children.

This is very common in Polish:

• Daję mamie prezent. = I give my mum a present.
• Mówię koledze prawdę. = I tell my friend the truth.

Dzieciom is the dative plural form of dzieci (children).

The verb czytać komuś coś means to read something to someone:

• komu? = to whom?
• co? = what?

In this sentence:

• dzieciom answers komu? = to the children
• krótką bajkę answers co? = a short story/fairy tale

So the structure is:

• czytam dzieciom bajkę = I read the children a story

Because bajkę is the direct object of the verb, so it is in the accusative case.

The verb czytać takes something being read:

• read what?
• bajkę

Since bajka is feminine singular, its accusative form is:

• bajka → bajkę

The adjective has to match the noun, so:

• krótka bajka = a short story/fairy tale (nominative)
• krótką bajkę = a short story/fairy tale (accusative)

Bajka most often means:

• fairy tale
• children’s story
• sometimes simply little story

In this sentence, because someone is reading to children, bajka sounds very natural as a children’s tale or a short story for children.

It is a bit more specific and child-oriented than a general word like historia or opowieść.

Because the preposition o meaning about requires the locative case.

So:

• las = forest
• o lesie = about the forest

and

• mały królik = little rabbit
• o małym króliku = about the little rabbit

So the phrase means:

• about the forest and a little rabbit

Yes, it looks a bit irregular at first.

The noun:

• las = forest

changes in the locative after o to:

• o lesie = about the forest

This kind of vowel change is normal in Polish and is something learners mostly have to get used to through exposure.

A few useful forms:

• las = forest
• w lesie = in the forest
• o lesie = about the forest

So even though the base word is las, the locative form is lesie.

Because after o meaning about, Polish uses the locative, not the accusative or genitive.

So:

• mały królik = little rabbit
• o małym króliku = about a little rabbit

Both the adjective and the noun must match in case:

• małym matches króliku
• both are in the locative singular

Compare:

• Widzę małego królika. = I see a little rabbit.
  
  • here it is accusative
• Czytam o małym króliku. = I am reading about a little rabbit.
  
  • here it is locative

Yes. I means and, so the story is described as being about:

• the forest
• and
• a little rabbit

It does not necessarily mean they are totally separate topics, just that both are part of the subject of the story.

So o lesie i małym króliku is naturally understood as:

• about the forest and a little rabbit

Yes. Polish word order is more flexible than English because the cases show the grammatical roles.

The original sentence:

• Po kolacji czytam dzieciom krótką bajkę o lesie i małym króliku.

is very natural.

But other orders are also possible, for example:

• Czytam dzieciom po kolacji krótką bajkę o lesie i małym króliku.
• Dzieciom czytam po kolacji krótką bajkę o lesie i małym króliku.
• Krótką bajkę o lesie i małym króliku czytam dzieciom po kolacji.

The meaning stays basically the same, but the focus changes. Polish often moves words around to emphasize time, object, or recipient.

Yes. Polish often leaves out subject pronouns when the verb ending already makes the subject clear.

• czytam = I read / I am reading

So there is no need to say ja unless you want emphasis.

Compare:

• Czytam dzieciom bajkę. = I read the children a story.
• Ja czytam dzieciom bajkę. = I am the one reading the children a story.

Using ja adds emphasis or contrast.

Yes, but it would change the meaning.

• czytać = imperfective, focusing on the activity/process
• przeczytać = perfective, focusing on completion

So:

• Po kolacji czytam dzieciom krótką bajkę...
  = After dinner, I read / am reading the children a short story...

but

• Po kolacji przeczytam dzieciom krótką bajkę...
  = After dinner, I will read the children a short story / I will finish reading it to them

A perfective verb in Polish cannot normally be used in the present tense for an ordinary present action; it usually refers to the future.

By itself, it could be either.

Polish czytam does not force one interpretation. So the sentence can mean:

• a habitual action: After dinner, I read the children a short story
• an action happening now in a current scene: After dinner, I’m reading the children a short story

Context decides.

If you wanted to make the habitual meaning clearer, you could add words like:

• zwykle = usually
• codziennie = every day

For example:

• Po kolacji zwykle czytam dzieciom krótką bajkę.

Królik literally means rabbit, but in many contexts, especially with children, it can also feel like bunny in English.

Because this sentence includes:

• małym króliku = little rabbit

it sounds gentle and child-friendly, so little bunny could be a natural English-style interpretation even though the basic dictionary meaning is rabbit.