Learn Hardcore German: Sie hat wegen ihrer Krankheit nicht lernen können und war deshalb nervös. - Because of her illness she was not able to study and was therefore nervous.

Wegen is a preposition that (traditionally) takes the genitive case.
The genitive (and dative) of the feminine noun die Krankheit is der Krankheit, and the corresponding possessive ihr becomes ihrer.

Nominative: ihre Krankheit (her illness – subject)
Accusative: ihre Krankheit (her illness – direct object)
Dative/Genitive: ihrer Krankheit

After wegen, we therefore need the genitive form: wegen ihrer Krankheit.

Note: In everyday speech, many Germans use the dative after wegen, but for feminine nouns the form looks the same in dative and genitive (ihrer Krankheit), so you can’t see the difference here anyway. For masculine/neuter, you would see it clearly, e.g.:

Standard: wegen seines Vaters (genitive)
Colloquial: wegen seinem Vater (dative)

Why is the verb phrase at the end nicht lernen können, and why in that order?

This is the perfect tense with a modal verb:

finite auxiliary: hat (in position 2)
non-finite verbs at the end: lernen können

In German perfect tense with a modal plus another verb, you usually get a “double infinitive” at the end:

Sie hat nicht lernen können. = She has not been able to study.

The order is:

Full verb (lernen)
Modal verb (können)

So: lernen können, not können lernen, when they both stand at the end in a perfect construction.

The negation nicht goes before the infinitive cluster to negate the whole activity: nicht lernen können = “to not be able to study”.

Why do we say hat ... nicht lernen können instead of konnte ... nicht lernen?

Both are grammatically correct:

Sie hat wegen ihrer Krankheit nicht lernen können. (perfect)
Sie konnte wegen ihrer Krankheit nicht lernen. (simple past)

Differences:

In spoken German, the perfect (hat nicht lernen können) is generally more common for most verbs.
For modal verbs like können, the simple past (konnte) is also very common, even in speech.

In terms of meaning, there is no real difference here in standard usage: both describe a past inability. Any nuance (result vs. narrative) is very weak in everyday language in this kind of sentence.

Why is there no form like gekonnt here in the perfect tense?

With modal verbs plus another verb, German very often uses the double infinitive instead of a past participle:

Common: Sie hat nicht lernen können.
Less common (but correct): Sie hat nicht lernen gekonnt.

So for many speakers, hat … lernen können simply is the usual perfect form of können when another verb like lernen is present. Gekonnt is most often used when können stands alone:

Das habe ich nicht gekonnt. – I wasn’t able to do that.

Why is hat used as the auxiliary and not ist?

In German, haben is used as the auxiliary for:

Transitive verbs (with a direct object)
Most intransitive verbs
All modal verbs, regardless of the main verb

Sein is only used with:

Verbs of movement from A to B (gehen, kommen, fahren, etc.)
Verbs of change of state (einschlafen, sterben, etc.)
The verbs sein and bleiben themselves in the perfect

Since the main verb group here is können / lernen, with a modal, the auxiliary must be haben: Sie hat nicht lernen können.

Why is war used (simple past) instead of ist ... gewesen (perfect)?

Both would be grammatically possible:

… und war deshalb nervös.
… und ist deshalb nervös gewesen. (less natural here)

However, in modern German:

The verbs sein and haben are very often used in the simple past even in spoken German.
Using war here is idiomatic and stylistically smooth.

Mixing perfect (hat … lernen können) and simple past (war) in one sentence is very normal in German. The whole sentence clearly refers to the past; tense choice here is more about style than strict aspect.

Why is nicht placed before lernen können and not somewhere else?

The placement of nicht shows what is being negated.

Sie hat wegen ihrer Krankheit nicht lernen können.
→ The ability to study is negated: she wasn’t able to study.

If you tried to put nicht in other positions, you’d either sound wrong or very unnatural:

✗ Sie hat wegen ihrer Krankheit lernen nicht können. – ungrammatical
✗ Sie hat nicht wegen ihrer Krankheit lernen können. – this would mean “It was not because of her illness that she couldn’t study,” which is a very different meaning.

So the standard pattern is:

[subject] + [auxiliary] + [adverbials like wegen ...] + nicht
- [infinitive cluster]

→ Sie hat wegen ihrer Krankheit nicht lernen können.

What does lernen mean here – “to study” or “to learn”?

In this context, lernen means roughly “to study” (for school, exams, homework):

lernen
- To learn (general)
- To study (especially for school, for a test, vocabulary, etc.)

Examples:

Ich muss für die Prüfung lernen. – I have to study for the exam.
Das Kind lernt Lesen. – The child is learning to read.

Be careful with studieren:

studieren means “to study at university” / “to major in”:
- Er studiert Medizin. – He studies medicine (at university).

So here, nicht lernen können almost certainly means “couldn’t study (for school/exams) because of her illness.”

What is the difference between wegen ihrer Krankheit and weil sie krank war?

Both express a cause, but in different structures:

Prepositional phrase:
- wegen ihrer Krankheit – because of her illness
- Short, noun-based, quite neutral/standard style.
Subordinate clause:
- weil sie krank war – because she was ill
- Full clause (with subject and verb), often a bit more explicit or narrative.

You could rephrase the sentence as:

Sie hat nicht lernen können, weil sie krank war, und war deshalb nervös.

Nuance: wegen + noun is slightly more compact and somewhat more formal than weil + sentence, but both are very common and natural.

How does deshalb work here, and where can it go in the sentence?

Deshalb is a sentence adverb meaning “therefore,” “for that reason.”

In a main clause, German must keep the finite verb in second position. You have two common options:

Deshalb in the first position:
- Sie hat wegen ihrer Krankheit nicht lernen können, und deshalb war sie nervös.
  (deshalb = position 1 → war must be position 2)
Deshalb in the midfield:
- Sie hat wegen ihrer Krankheit nicht lernen können und war deshalb nervös.
  (here und connects the verbs; war is already in 2nd position, deshalb comes after it)

Both are correct. The given sentence uses option 2.

You cannot move deshalb to the very end in a normal way (… und war nervös deshalb sounds odd in standard German). It usually appears near the beginning or in the “midfield” (after the verb but before most complements).

What is the difference between deshalb, deswegen, and darum?

All three can usually be translated as “therefore / for that reason / so” and are often interchangeable:

Sie war krank, deshalb war sie nervös.
Sie war krank, deswegen war sie nervös.
Sie war krank, darum war sie nervös.

Differences:

deshalb and deswegen are very close in meaning and style; deshalb is perhaps slightly more common in neutral written German.
darum is also common and can sound a bit more conversational in some regions, but is fully standard.

In this sentence, you could replace deshalb with deswegen or darum without changing the meaning.

Is Sie here she or polite you?

At the beginning of a sentence, Sie (she) and Sie (formal you) look the same because everything is capitalized anyway. You have to use context.

The key clue is ihrer Krankheit:

For she / her illness, you write: ihrer Krankheit (lowercase i)
For polite you / your illness, you would write: Ihrer Krankheit (capital I, because formal-address pronouns are capitalized)

In the given sentence, it is ihrer Krankheit with a lowercase i, so this clearly refers to “her illness” → Sie = she.

Why is there no comma before und in this sentence?

German comma rules differ from English. Here we have:

One subject: Sie
A compound predicate:
- hat … nicht lernen können
- war … nervös

Connected by und within a single main clause. In this case, no comma is required:

Sie hat … nicht lernen können und war deshalb nervös.

You would use a comma before und if you were clearly joining two separate main clauses with their own subjects, or if a comma is needed for a subordinate clause, list, etc. Here, it’s just a shared subject with two verb groups, so no comma.