Learn Hardcore German: Ein Muttersprachler korrigiert meinen Akzent sehr geduldig. - A native speaker corrects my accent very patiently.

Ein Muttersprachler = “A native speaker” (subject → nominative).
Einen Muttersprachler would be accusative, used for a direct object, e.g.:
- Ich sehe einen Muttersprachler. – I see a native speaker.

In your sentence, the native speaker is doing the correcting, so nominative ein, not accusative einen.

Why is Muttersprachler capitalized?

In German, all nouns are capitalized, regardless of where they appear in the sentence.

Muttersprachler is a noun meaning “native speaker,” so it is written with a capital M:

der Muttersprachler – (male) native speaker
die Muttersprachlerin – (female) native speaker
die Muttersprachler – native speakers (plural, mixed or all male)
die Muttersprachlerinnen – female native speakers (plural)

What gender is Muttersprachler, and does that affect the article ein?

Muttersprachler is masculine (grammatically).

Singular nominative masculine indefinite article: ein
- ein Muttersprachler korrigiert …

If you want to explicitly talk about a woman, you use the feminine form:

eine Muttersprachlerin korrigiert meinen Akzent sehr geduldig.

So the gender of the noun determines both the form of the noun (-er vs -in) and the article (ein vs eine).

Why is it meinen Akzent and not mein Akzent?

Because Akzent is:

Masculine: der Akzent
The direct object (= what is being corrected), so it must be in the accusative case.

For masculine nouns, the possessive mein changes in the accusative:

Nominative: mein Akzent (my accent – as subject)
Accusative: meinen Akzent (my accent – as object)

Examples:

Mein Akzent ist schlecht. – My accent is bad. (subject → nominative)
Er korrigiert meinen Akzent. – He corrects my accent. (object → accusative)

What case is meinen Akzent, and how can I recognize it?

Meinen Akzent is in the accusative case.

Clues:

It is the thing directly affected by the verb korrigiert → it answers “What does he correct?”
- He corrects what? → meinen Akzent.
Masculine accusative often shows -en on the article or possessive:
- den Akzent, einen Akzent, meinen Akzent, seinen Akzent, etc.

So, subject (nominative) = ein Muttersprachler, direct object (accusative) = meinen Akzent.

Why isn’t there a pronoun like mich in the sentence?

In English you might say:

“A native speaker corrects me very patiently.”

German, however, usually specifies what is corrected:

Ein Muttersprachler korrigiert meinen Akzent sehr geduldig.

Here, meinen Akzent already shows who is involved (my accent → mine). A separate mich would be unusual and not idiomatic in this exact structure.

You can use mich with this verb, but in a different construction:

Ein Muttersprachler korrigiert mich sehr geduldig. – A native speaker corrects me very patiently.
- Here, mich is the direct object, and Akzent is not mentioned.

So you typically choose either the person (mich) or the thing that gets corrected (meinen Akzent), not both together.

Why is the verb form korrigiert and not korrigieren or something else?

Korrigieren is the infinitive (“to correct”).

The subject is ein Muttersprachler = third person singular (“he/she/it”). German verbs in the present tense take the ending -t in 3rd person singular:

ich korrigiere
du korrigierst
er / sie / es korrigiert
wir korrigieren
ihr korrigiert
sie korrigieren

So with ein Muttersprachler (he), the correct form is korrigiert.

Does korrigiert mean “is correcting” or “corrects”? How do I express that in German?

German Präsens (present tense) covers both:

A general habit:
Ein Muttersprachler korrigiert meinen Akzent sehr geduldig.
→ A native speaker corrects my accent very patiently. (whenever we speak)
An action happening right now:
Ein Muttersprachler korrigiert gerade meinen Akzent.
→ A native speaker is (right now) correcting my accent.

To make “right now” clearer, German adds words like gerade, im Moment, jetzt:

Ein Muttersprachler korrigiert gerade meinen Akzent sehr geduldig.

Can the word order with sehr geduldig be different? Where can I put it?

Your version is the most natural:

Ein Muttersprachler korrigiert meinen Akzent sehr geduldig.

Other possibilities are grammatically correct but sound more marked or slightly unusual in neutral speech:

Ein Muttersprachler korrigiert sehr geduldig meinen Akzent.
(Focus more on how he corrects, less on what.)
Sehr geduldig korrigiert ein Muttersprachler meinen Akzent.
(Stylistic, emphasizes “very patiently”, sounds a bit poetic or written.)

General rule: in German main clauses, the verb usually stays in position 2, and adverbials like sehr geduldig often appear towards the end of the sentence, after the object.

What exactly does sehr geduldig mean, and how is it different from just geduldig?

geduldig = patient(ly)
sehr geduldig = very patient(ly)

So sehr intensifies the adjective/adverb:

Er ist geduldig. – He is patient.
Er ist sehr geduldig. – He is very patient.
Er korrigiert meinen Akzent geduldig. – He corrects my accent patiently.
Er korrigiert meinen Akzent sehr geduldig. – He corrects my accent very patiently.

Sehr is used like “very” in English to strengthen adjectives and adverbs.

Could I also say verbessert instead of korrigiert? What is the difference?

Both are possible, but there is a nuance:

korrigieren = to correct mistakes, to point out and fix errors.
- Ein Muttersprachler korrigiert meinen Akzent.
  → He notices what is wrong and corrects it.
verbessern = to improve, make something better (not always focusing on clear “errors”).
- Ein Muttersprachler verbessert meinen Akzent.
  → He helps my accent become better, maybe in a more general way.

In most learning contexts, korrigieren is more precise when someone is actively pointing out specific pronunciation errors.