Den Verband, den sie mir gegeben hat, soll ich morgen wechseln; die Spritze brauche ich zum Glück nicht.

German often moves something other than the subject to the front for topic or emphasis. Here, Den Verband is being highlighted as the thing under discussion.

A more neutral version would be:

Ich soll den Verband, den sie mir gegeben hat, morgen wechseln.

So the original does not change the basic meaning; it just makes the bandage/dressing the starting point of the sentence.

The two dens are doing different jobs:

• the first den is the article of Verband
• the second den is a relative pronoun, meaning that/which

So:

• Den Verband = the bandage/dressing
• den sie mir gegeben hat = that she gave me

The second den refers back to Verband.

Because the relative pronoun takes its case from its role inside the relative clause, not from English word order.

Inside the clause, the bandage is the direct object of gegeben hat:

Sie hat mir den Verband gegeben.

Since Verband is masculine singular, its accusative form is den.

So the relative clause uses den, not der.

Because German always sets off relative clauses with commas.

So:

Den Verband, den sie mir gegeben hat, soll ich morgen wechseln.

This is different from English, where that she gave me often has no comma.

Because relative clauses are a type of subordinate clause, and in German subordinate clauses send the finite verb to the end.

So:

• main clause: sie hat mir den Verband gegeben
• relative clause: den sie mir gegeben hat

In the perfect tense, you usually get:

• participle first: gegeben
• auxiliary last: hat

mir is the dative form of ich, and here it means to me.

In sie mir gegeben hat, the roles are:

• sie = subject
• mir = indirect object
• den Verband = direct object

So literally: she gave me the bandage/dressing.

Here sollen usually means to be supposed to, to be expected to, or to have been told to do something.

So soll ich morgen wechseln is best understood as:

• I’m supposed to change it tomorrow
• I’m meant to change it tomorrow

English should is sometimes used in translation, but it can sound like advice. German sollen often suggests an outside instruction or recommendation.

Because German main clauses follow the verb-second rule.

The whole fronted phrase

Den Verband, den sie mir gegeben hat

counts as the first element in the sentence. That means the finite verb must come next:

Den Verband, den sie mir gegeben hat, soll ich morgen wechseln.

So the order is:

1. fronted object phrase
2. soll
3. ich
4. the rest

In a medical context, einen Verband wechseln means to change a bandage/dressing.

So wechseln here means replace/change, not something abstract like switching opinions or changing trains.

Also, Verband in this context is usually better understood as bandage or dressing, depending on the situation.

In everyday medical German, die Spritze often means the injection/shot, not just the physical syringe.

So here:

die Spritze brauche ich zum Glück nicht

most naturally means:

Luckily, I don’t need the injection/shot.

For the same reason Den Verband is fronted in the first clause: emphasis and contrast.

The sentence is contrasting two medical things:

• the bandage/dressing: I have to change it
• the injection: luckily, I don’t need it

A more neutral order would be:

Ich brauche die Spritze zum Glück nicht.

But fronting die Spritze gives it extra focus.

zum Glück means luckily or fortunately.

In this sentence:

die Spritze brauche ich zum Glück nicht

it comments on the whole statement: fortunately, the injection is not necessary.

Its position is fairly flexible. For example:

• Zum Glück brauche ich die Spritze nicht.
• Ich brauche die Spritze zum Glück nicht.
• Die Spritze brauche ich zum Glück nicht.

All are natural, with slightly different emphasis.

The semicolon links two independent but closely related clauses:

• Den Verband ... soll ich morgen wechseln
• die Spritze brauche ich zum Glück nicht

A semicolon is stronger than a comma but weaker than a full stop.

You could also write:

• Den Verband, den sie mir gegeben hat, soll ich morgen wechseln. Die Spritze brauche ich zum Glück nicht.
• Den Verband, den sie mir gegeben hat, soll ich morgen wechseln, aber die Spritze brauche ich zum Glück nicht.

A less marked version would be:

Ich soll den Verband, den sie mir gegeben hat, morgen wechseln; ich brauche die Spritze zum Glück nicht.

The original is perfectly natural, but it sounds more focused and contrastive because it puts Den Verband and die Spritze first.