Learn Hardcore German: Ich schreibe ein kurzes Gedicht und übe damit den Satzbau. - I write a short poem and use it to practise sentence structure.

Article: neuter accusative singular after ein stays ein (same as nominative).
Adjective ending: neuter accusative singular after ein takes -es → kurz → kurzes.

So we get:
Ich schreibe ein kurzes Gedicht.
(Ich = subject, ein kurzes Gedicht = accusative object.)

You cannot use eine (feminine) or einen (masculine accusative) because those would require a feminine or masculine noun.

Why is it den Satzbau and not der Satzbau or dem Satzbau?

The verb üben takes a direct object in the accusative case:

etwas üben = to practice something

Satzbau (sentence structure) is a masculine noun: der Satzbau.

Masculine accusative singular uses den:

Nominative: der Satzbau
Accusative: den Satzbau

So after übe we need the accusative → den Satzbau:

Ich übe den Satzbau. = I practice the sentence structure.

Dem Satzbau would be dative (e.g. mit dem Satzbau), which doesn’t fit after üben in this meaning.

What does damit mean here, and why isn’t it so that?

Damit has two main uses in German:

As a conjunction meaning so that, introducing a subordinate clause:
- Ich schreibe ein Gedicht, damit ich den Satzbau übe.
  = I write a poem so that I (can) practice sentence structure.
As a pronoun/adverb meaning with it / with that, referring back to something already mentioned:
- Ich schreibe ein kurzes Gedicht und übe damit den Satzbau.
  = I write a short poem and with that I practice sentence structure.

In your sentence, damit belongs to type 2: it refers back to ein kurzes Gedicht and literally means with it or by means of it.

So here it does not introduce a new clause; it just stands inside the clause as an object-like element.

Why is the word order und übe damit den Satzbau and not und damit übe den Satzbau?

German main clauses normally have the conjugated verb in second position (the famous "V2 rule").

After the coordinating conjunction und, a new main clause starts:

Ich (1st position)
schreibe (2nd: finite verb)
ein kurzes Gedicht (rest of the clause)
und
[ich] (understood subject)
übe (2nd: finite verb)
damit den Satzbau (rest of the clause)

So:

… und übe damit den Satzbau. ✅ (verb is 2nd element in its clause)
… und damit übe den Satzbau. ❌ (here übe would be 3rd)

You can make damit the first element of the second clause if you want to emphasize it, but then the verb has to move to 2nd position:

… und damit übe ich den Satzbau. ✅ (now damit is position 1, übe is position 2)

Could I say Ich schreibe ein kurzes Gedicht, um den Satzbau zu üben instead? Is there a difference?

Yes, that is correct German, and the meaning is very close, but there is a nuance:

Ich schreibe ein kurzes Gedicht und übe damit den Satzbau.
= I write a short poem and with that I practice sentence structure.
→ Two coordinated actions; the second uses the first as a means.
Ich schreibe ein kurzes Gedicht, um den Satzbau zu üben.
= I write a short poem in order to practice sentence structure.
→ Stronger focus on purpose (the reason WHY you write the poem).

In everyday conversation, both are natural; the um … zu construction highlights intention a bit more clearly.

Why is the adjective kurz changed to kurzes?

In German, adjectives before a noun take an ending that shows case, gender, and number.

Here:

Noun: Gedicht → das Gedicht (neuter)
Role: direct object → accusative
Article: ein (indefinite article)

Pattern for neuter accusative singular with ein is:

ein
- adjective -es
  - noun
    → ein kurzes Gedicht

So:

ein kurzes Gedicht (accusative, neuter)
ein kurzes Gedicht (nominative, neuter) – same form here

Compare:

ein kurzer Satz (masculine nominative)
einen kurzen Satz (masculine accusative)
eine kurze Frage (feminine nominative/accusative)

Why is it Ich schreibe and not something like I am writing? How does German express the continuous?

German usually doesn’t have a separate continuous tense like English I am writing.

The simple present in German (ich schreibe) can express:

English I write
or I am writing
or even I will write (in some contexts)

So Ich schreibe ein kurzes Gedicht can mean:

I write a short poem.
I am writing a short poem (right now).

Context tells you which one is intended.

Is Satzbau always used with an article, like den Satzbau, or can you omit it?

It depends on context, but in a sentence like this, using the article is normal and idiomatic:

Ich übe den Satzbau. ✅

You could sometimes see Satzbau üben without an article in titles, notes, or very general statements (like a label: "Satzbau üben" on a worksheet). But in a full sentence with ich, learners usually say:

Ich übe den Satzbau.

If you wanted to speak more generally, you could rephrase:

Ich übe die Satzstruktur. (also with article)
Ich übe Grammatik. (here Grammatik is often used without an article because it’s uncountable and abstract.)

Can damit be placed at the end, like … und übe den Satzbau damit?

Yes, that is also grammatically correct:

… und übe damit den Satzbau. ✅
… und übe den Satzbau damit. ✅

Both are used. The difference is slight:

übe damit den Satzbau: damit is closer to the verb, a bit more neutral.
übe den Satzbau damit: slight emphasis on den Satzbau, because it’s closer to the verb and often feels a bit more "heavy" at the end.

In everyday speech, both orders sound fine and natural. Word order of pronouns vs. nouns and emphasis can influence which one a native speaker chooses, but here there is no big meaning difference.

Is und changing the word order like some other German conjunctions do?

No. Und is a coordinating conjunction. It connects two main clauses and does not change the word order rule:

Clause 1: Ich schreibe ein kurzes Gedicht.
Clause 2: Ich übe damit den Satzbau.

Joined:

Ich schreibe ein kurzes Gedicht und übe damit den Satzbau.

In each main clause, the finite verb stays in second position.

Conjunctions that do send the verb to the end of the clause (like weil, dass, damit when used as conjunctions) are subordinating conjunctions, not like und.