Když moje dcera udělá chybu, vezme gumu a napíše odpověď znovu.

Because these are perfective verbs: udělat, vzít/vezme, napsat.

In Czech, perfective verbs do not normally describe an action happening right now. Their present-tense forms usually refer to a complete action. In English, that often gets translated as:

• a future action: napíše = she will write
• or, after words like když, as a general present: Když udělá chybu... = When/Whenever she makes a mistake...

So the Czech is natural here because it presents each action as a complete event:

1. she makes a mistake,
2. she takes an eraser,
3. she writes the answer again.

Udělat chybu is the normal way to say to make a mistake when you mean one completed mistake.

• udělat chybu = make a mistake
• dělat chyby = make mistakes, be making mistakes, make them repeatedly/in general

Here the sentence is about one specific mistake each time, so udělá chybu fits better.

Because chybu is the accusative singular form of chyba.

The verb udělat takes a direct object, and direct objects are usually in the accusative:

• chyba = mistake (dictionary form, nominative)
• udělat chybu = to make a mistake (accusative)

So chybu is required by the grammar of the sentence.

For the same reason: gumu is the accusative singular of guma, because it is the direct object of vezme.

• guma = eraser / rubber
• vezme gumu = she takes an eraser

In school context, guma commonly means eraser.

It is in the accusative too, but for this noun the nominative and accusative singular have the same form.

• odpověď = answer
• napíše odpověď = she writes the answer

So the case changes grammatically, but the word itself does not visibly change.

Czech has no articles. There is no separate word that automatically corresponds to English a/an or the.

So:

• vezme gumu can mean she takes an eraser or she takes the eraser
• napíše odpověď can mean she writes an answer or the answer

The exact meaning is usually clear from context. If Czech needs to be more explicit, it can use words like ten or jeden, but that is not necessary here.

Because Czech often omits subject pronouns when they are already clear from the verb form.

• vezme already means he/she will take
• napíše already means he/she will write

Since moje dcera has already been mentioned, there is no need to repeat ona. If you add ona, it usually gives extra emphasis or contrast.

Because Když moje dcera udělá chybu is a subordinate clause introduced by když.

In Czech, subordinate clauses are normally separated by a comma from the main clause:

• Když moje dcera udělá chybu, vezme gumu...

This is standard Czech punctuation.

Literally, když means when, but in a sentence like this it often has the sense of whenever.

So this sentence can be understood as:

• When my daughter makes a mistake...
• or more naturally in English, Whenever my daughter makes a mistake...

It describes what usually happens in that situation, not just one unique event.

Yes. Both are possible.

• má dcera = my daughter
• moje dcera = my daughter

Moje dcera is very common in everyday speech. Má dcera is also correct, but can sound a bit shorter, more formal, or more literary depending on context. In this sentence, moje dcera sounds perfectly natural.

Yes, you could hear other options, but znovu is a very standard choice here.

• znovu = again, anew
• znova = again, very common in speech
• zase = again, but often a bit broader in meaning

In this sentence, znovu fits well because she is writing the answer again after correcting it.

Yes, Czech word order is flexible.

For example, you could put the main clause first, but the original order is very natural because it sets up the situation first:

• Když moje dcera udělá chybu, vezme gumu a napíše odpověď znovu.

This feels like:

1. first the mistake happens,
2. then she reacts.

So the chosen word order is not random; it matches the logic of the action.