Du brauchst den Pfirsich nicht zu schälen; er ist schon gewaschen.

Because Pfirsich is the direct object of brauchst.

• der Pfirsich = nominative masculine, used for the subject
• den Pfirsich = accusative masculine, used for the direct object

Here, du is the subject, and den Pfirsich is the thing you do not need to peel.

This is a very common German structure:

brauchen + nicht + zu + infinitive

It means do not need to do something.

So:

• Du brauchst den Pfirsich nicht zu schälen = You do not need to peel the peach

In standard German, brauchen is often used this way in negative sentences or questions.

Because the negation applies to the whole action zu schälen.

German normally says:

• Du brauchst ... nicht zu schälen

This means you do not need to peel it.

The important pattern to remember is:

• nicht zu + infinitive

So the negation comes before the zu-infinitive phrase.

It behaves a bit like a modal verb, but it is not a full modal verb in the same way as müssen, können, or dürfen.

Why learners notice this:

• It combines with another verb
• That second verb goes to the end
• It expresses necessity

But unlike the true modal verbs, brauchen usually takes zu:

• Du musst den Pfirsich schälen
• Du brauchst den Pfirsich nicht zu schälen

So it is often called a semi-modal or modal-like verb.

Because in German main clauses, the conjugated verb usually comes in second position, while the infinitive part goes to the end.

Here:

• brauchst = conjugated verb, so it comes early
• zu schälen = infinitive phrase, so it goes to the end

This is normal German word order.

Here, er refers back to der Pfirsich.

Since Pfirsich is a masculine noun, the pronoun is:

• er = he / it

In English, we say it, but German nouns always have grammatical gender, so a peach is referred to as er.

Because er is the subject of the second clause:

• er ist schon gewaschen

The peach is the thing that is already washed, so it must be in the nominative case:

• er = nominative
• ihn = accusative

If you used ihn, it would mean the peach was an object, not the subject.

Gewaschen is the past participle of waschen.

Here it is used with ist to describe a state/result:

• er ist gewaschen = it is washed

This is very common in German when describing the condition something is in.

Compare:

• Er wird gewaschen. = it is being washed
• Er ist gewaschen. = it is washed / it has been washed

So this sentence focuses on the result: the peach is already in a washed state.

Here, schon means already.

So:

• er ist schon gewaschen = it is already washed

It tells you that the washing has already happened before now.

The semicolon connects two closely related independent clauses:

• Du brauchst den Pfirsich nicht zu schälen
• er ist schon gewaschen

A semicolon is stronger than a comma but weaker than a period. It shows that the second clause explains or supports the first one.

You could also write:

• Du brauchst den Pfirsich nicht zu schälen, denn er ist schon gewaschen.
• Du brauchst den Pfirsich nicht zu schälen. Er ist schon gewaschen.

All are possible, but the semicolon gives a neat written connection.

Yes, that is possible, and it often means the same thing: You do not have to peel the peach.

However, brauchen ... nicht zu is often clearer and more natural for expressing no need.

So:

• Du brauchst den Pfirsich nicht zu schälen = very clear there is no need to peel it
• Du musst den Pfirsich nicht schälen = also common, but learners are often taught brauchen ... nicht zu as the most direct equivalent of do not need to

Du is the informal singular word for you.

So this sentence sounds like you are speaking:

• to one person
• informally

Other versions would be:

• Ihr braucht den Pfirsich nicht zu schälen = talking informally to more than one person
• Sie brauchen den Pfirsich nicht zu schälen = formal singular or plural

So the choice of du tells you about the relationship and number, not about the basic grammar of the sentence.