Später repariert mein Bruder den Tacker, und ich benutze den Kleber für das Plakat.

Because German main clauses follow the verb-second rule.

That means the finite verb must come in the second position in the clause. Here, Später takes the first position, so the verb repariert must come next:

• Später = position 1
• repariert = position 2
• mein Bruder = after the verb

This is very common in German:

• Ich repariere den Tacker.
• Später repariere ich den Tacker.
• Heute benutzt sie den Kleber.

So when something like Später, Heute, or Dann starts the sentence, the subject usually comes after the verb.

German often uses the simple present tense to talk about the future, especially when there is a clear time word such as später.

So:

• Später repariert mein Bruder den Tacker
  can mean
• Later, my brother repairs the stapler
  or more naturally in English,
• Later, my brother will repair the stapler

The same idea applies to ich benutze. German does not always need a special future form when the time is already clear from context.

German does have a future construction with werden, but it is often unnecessary:

• Später wird mein Bruder den Tacker reparieren.

That is correct too, but the present tense is usually more natural in everyday German.

Because Bruder is masculine singular nominative, and the possessive determiner mein follows the same pattern as ein.

In the nominative masculine singular, these words usually have no ending:

• mein Bruder
• dein Bruder
• sein Bruder
• ein Bruder

Compare that with other cases or genders:

• meine Schwester (feminine nominative)
• mein Kind (neuter nominative)
• meinen Bruder (masculine accusative)

So mein Bruder is the correct form because it is the subject of the clause.

Because both nouns are being used as direct objects, and both are masculine singular nouns. In German, masculine singular nouns change their article in the accusative case:

• nominative: der
• accusative: den

So:

• der Tacker → den Tacker
• der Kleber → den Kleber

They are accusative here because they are the things being acted on:

• my brother repairs the stapler
• I use the glue

This is one of the most important German case patterns to learn.

They are the things directly affected by the verbs.

Ask the question What is being repaired?
→ den Tacker

Ask What am I using?
→ den Kleber

Those are direct objects, and direct objects in German usually take the accusative case.

So in this sentence:

• mein Bruder = subject
• den Tacker = direct object
• ich = subject
• den Kleber = direct object

Because the preposition für always takes the accusative case.

The noun Plakat is neuter, so:

• nominative: das Plakat
• accusative: das Plakat

For neuter nouns, nominative and accusative look the same, so you still see das.

So:

• für das Plakat = for the poster

Here, für das Plakat explains the purpose of the glue: the glue is being used for the poster.

No. Und is a coordinating conjunction, so the clause after it keeps normal main-clause word order.

That is why we get:

• ..., und ich benutze den Kleber ...

The subject ich comes before the verb benutze, because this second clause is a regular main clause.

This is different from subordinating conjunctions like weil or dass, which send the verb to the end:

• ..., weil ich den Kleber benutze.

So with und, you do not move the verb to the end.

Because the second part is still a main clause, not a subordinate clause.

German main clauses keep the finite verb in second position:

• ich benutze den Kleber

Only certain conjunctions, such as weil, dass, or wenn, push the verb to the end.

So:

• und ich benutze den Kleber = main clause word order
• weil ich den Kleber benutze = subordinate clause word order

Normally, später is written with a lowercase s, because it is an adverb, not a noun.

It is capitalized here only because it is the first word of the sentence:

• Später repariert mein Bruder ...

If it appeared in the middle of a sentence, it would usually be lowercase:

• Mein Bruder repariert den Tacker später.

So the capitalization here is just standard sentence-initial capitalization.

Yes, German word order is somewhat flexible, but the finite verb must still stay in second position in a main clause.

For example, these are possible:

• Mein Bruder repariert später den Tacker, und ich benutze den Kleber für das Plakat.
• Den Tacker repariert mein Bruder später, und ich benutze den Kleber für das Plakat.

These versions change the focus or emphasis, but the basic meaning stays similar.

The original sentence is very natural because it starts with the time word Später, which sets the scene nicely.

Yes, you should memorize each noun together with its article:

• der Tacker
• der Kleber
• das Plakat

German noun gender is important because it affects:

• articles
• adjective endings
• pronouns
• case forms

For example:

• der Tacker → den Tacker
• der Kleber → den Kleber
• das Plakat → das Plakat

A very good habit is to learn nouns as full units, not by themselves:

• not just Tacker
• but der Tacker

That will make case endings much easier later.