Im Waggon zieht sie den Ärmel hoch, weil ihr Ellbogen noch weh tut.

Im is just the normal contraction of in dem.

Here, in means location, not movement, so it takes the dative case:

• der Waggon → dem Waggon
• in dem Waggon → im Waggon

A useful contrast:

• im Waggon = in the carriage
• in den Waggon = into the carriage

Waggon means a rail carriage or train car.

It is a correct word, but it can sound a bit traditional or formal to some learners. You may also see Wagon as a spelling variant. In everyday German, people often use other train-related words depending on context, but Waggon is perfectly understandable.

Because den Ärmel is the direct object of zieht.

The verb here is hochziehen / ziehen ... hoch, and the thing being pulled up is the sleeve. Since Ärmel is masculine (der Ärmel), the accusative form is den Ärmel.

So:

• nominative: der Ärmel
• accusative: den Ärmel

German often uses the definite article with body parts and clothing when it is already clear whose body part or clothing is meant.

So sie zieht den Ärmel hoch is very natural. The context already tells us it is her sleeve.

Using ihren Ärmel is possible, but it gives more emphasis to possession, for example if you want to contrast it with someone else’s sleeve.

This is a separable verb structure.

The full verb is hochziehen, which here means something like pull up. In a main clause, separable verbs split:

• Sie zieht den Ärmel hoch.

So:

• zieht = the conjugated verb part
• hoch = the separable prefix/particle, placed later in the clause

In the infinitive, it is written together:

• den Ärmel hochziehen

Not exactly.

Den Ärmel hochziehen literally means pull the sleeve up. It can describe simply moving the sleeve upward so the elbow is exposed.

If you specifically mean roll up in the sense of folding it up, German often uses aufkrempeln:

• den Ärmel aufkrempeln

So hochziehen is a bit more general and physical: she pulls it up.

Because weil introduces a subordinate clause, and in subordinate clauses the conjugated verb goes to the end.

Compare:

Main clause:

• Ihr Ellbogen tut noch weh.

Subordinate clause:

• ..., weil ihr Ellbogen noch weh tut.

So the basic pattern is:

• weil
  • subject + other elements + verb at the end

Here, weh tut belongs together as the predicate, and tut is the finite verb that goes to the end.

Here, ihr means her. It is a possessive determiner modifying Ellbogen.

So:

• ihr Ellbogen = her elbow

It is not the dative pronoun to her in this sentence.

A different structure would be:

• weil ihr der Ellbogen noch weh tut

That version means essentially the same thing, but there ihr really is a dative pronoun.

Weh tun is a very common German expression meaning to hurt.

Examples:

• Mein Arm tut weh.
• Der Ellbogen tut noch weh.

German also has the verb schmerzen, but weh tun is often more common in everyday speech.

Very roughly:

• Das schmerzt. = more formal/literary/medical-sounding
• Das tut weh. = very common everyday German

You will often see weh tun written as two words in forms like this:

• Der Arm tut weh.
• ..., weil der Arm weh tut.

That is very common and natural.

You may also come across wehtun / wehtut as a single written form in dictionaries or other texts, but in normal sentence patterns like this, the separated form weh tut is extremely common and usually the safest one for learners to recognize.

Noch means still here.

So ihr Ellbogen tut noch weh means that the elbow was already hurting before, and the pain continues now.

Without noch, the sentence would simply state that it hurts. With noch, it emphasizes that the problem has not gone away yet.

Yes. Ellbogen and Ellenbogen are variants of the same word: elbow.

Both are understood, and Ellenbogen is often the form learners meet first. The shorter form Ellbogen is also standard and completely normal.