Meine Sprachpartnerin kommt aus Wien, deshalb höre ich gern ihren Akzent.

Sprachpartnerin is a feminine noun meaning a female language partner or language-exchange partner.

German often shows that a person is female by adding -in:

• der Sprachpartner = male language partner
• die Sprachpartnerin = female language partner

It is also a compound noun:

• Sprache = language
• Partnerin = female partner

So Sprachpartnerin is literally something like language partner.

Because Sprachpartnerin is feminine and it is the subject of the clause, so it is in the nominative singular.

The possessive word mein- changes its ending depending on gender, case, and number. Here it takes -e:

• mein Sprachpartner = my male language partner
• meine Sprachpartnerin = my female language partner

So meine is the correct form for a feminine noun in this position.

Aus is the normal preposition for saying where someone is from, especially with cities, regions, and countries.

So:

• aus Wien = from Vienna
• aus Deutschland = from Germany
• aus der Schweiz = from Switzerland

German very often uses kommen aus to express origin:

• Sie kommt aus Wien. = She is from Vienna.

With Wien, there is no article, so it is simply aus Wien.

The sentence has two main clauses:

• Meine Sprachpartnerin kommt aus Wien
• deshalb höre ich gern ihren Akzent

In German, it is very common to separate main clauses with a comma. The comma marks a pause and shows that the second clause is connected to the first one logically.

You could also separate them with a full stop or semicolon in many contexts, but the comma is very normal here.

Because in a German main clause, the finite verb must be in second position.

Here, deshalb takes the first position. That means the verb höre must come immediately after it, and the subject ich comes next:

• Deshalb höre ich ...

This is a very common pattern:

• Heute gehe ich nach Hause.
• Dann machen wir weiter.
• Deshalb höre ich gern ihren Akzent.

So the important rule is: if something other than the subject comes first, the verb still stays in second position.

Not exactly.

Deshalb means therefore / that is why / for that reason. It starts a new main clause, so normal main-clause word order applies:

• Meine Sprachpartnerin kommt aus Wien, deshalb höre ich gern ihren Akzent.

Weil means because. It introduces a subordinate clause, and the conjugated verb goes to the end:

• Ich höre gern ihren Akzent, weil meine Sprachpartnerin aus Wien kommt.

Both sentences can express a similar idea, but the grammar is different.

Yes. Gern and gerne are both correct. Gern is just the shorter form and is very common in everyday German.

With verbs, gern/gerne often expresses the idea of liking to do something:

• Ich lese gern. = I like reading.
• Ich höre gern ihren Akzent. = I like hearing her accent.

So here, gern does not describe the noun Akzent. It describes the action höre.

Because Akzent is the direct object of höre, and hören takes the accusative case.

Akzent is a masculine noun:

• der Akzent = nominative
• den Akzent = accusative

The possessive determiner based on ihr- changes too:

• ihr Akzent = her accent, as subject
• ihren Akzent = her accent, as direct object

So in this sentence, ihren Akzent is correct because the speaker is hearing the accent.

Here it means her, because it refers back to meine Sprachpartnerin, one female person.

But yes, forms of ihr- can be ambiguous in other contexts. Depending on context, they can mean:

• her
• their
• sometimes formal your forms exist too, but with capital letters in writing: Ihr, Ihren, etc.

In this sentence, the meaning is clear from context: their accent would not match meine Sprachpartnerin.

Because Akzent is a noun, and in German all nouns are capitalized.

So in this sentence:

• Sprachpartnerin is capitalized
• Wien is capitalized
• Akzent is capitalized

This is a general rule in German, not something special about this sentence.