Learn Hardcore German: Der Bauer repariert den Stall, während die Schafe ruhig auf der Wiese stehen. - The farmer repairs the stable while the sheep stand calmly in the meadow.

Der Bauer is the subject of the sentence → nominative case.
- Masculine nominative singular: der Bauer
den Stall is the direct object (the thing being repaired) → accusative case.
- Masculine accusative singular: den Stall

So:

der Bauer (who is doing something)
den Stall (what he is repairing)

Why is it auf der Wiese and not auf die Wiese?

The preposition auf can take dative or accusative, depending on meaning:

Dative = location (where something is)
Accusative = direction / movement (where something is going)

In this sentence, the sheep are just standing on the meadow (location, no movement), so we use dative:

Feminine noun die Wiese
Feminine dative singular: der Wiese
→ auf der Wiese = on the meadow (where?)

If we had movement, it would be accusative:

auf die Wiese = onto the meadow (to where?)

Why is the verb stehen at the very end: …auf der Wiese stehen?

Because of the conjunction während.

während introduces a subordinate clause. In German subordinate clauses, the finite verb goes to the end of the clause:

Main clause: Der Bauer repariert den Stall.
→ Normal word order: verb in 2nd position (repariert).
Subordinate clause with während:
…während die Schafe ruhig auf der Wiese stehen.
→ Verb stehen goes to the end.

Pattern:
[Subordinating conjunction] + [subject] + [other elements] + [verb at the end]

Why is there a comma before während?

The sentence contains two clauses:

Der Bauer repariert den Stall (main clause)
während die Schafe ruhig auf der Wiese stehen (subordinate clause)

In German, main and subordinate clauses are separated by a comma. So the comma before während is mandatory.

Why is it ruhig and not ruhige?

ruhig here is functioning as an adverb, not as an adjective before a noun.

As an adverb, it stays in its basic form: ruhig
- It describes how the sheep are standing: they are standing calmly.
With a noun, as an attributive adjective, it would take an ending:
- die ruhigen Schafe = the calm sheep
- ein ruhiges Schaf = a calm sheep

In the sentence we have:

die Schafe stehen ruhig → ruhig modifies the verb stehen.

Why is it die Schafe and not der Schafe or den Schafe?

Schafe is plural of das Schaf (sheep).

Nominative singular: das Schaf
Nominative plural: die Schafe

In the subordinate clause, die Schafe are the subject → nominative plural:

die Schafe stehen … = the sheep are standing …

For plural nouns in the nominative, die is always used (for all genders):

die Schafe (the sheep)
die Kinder (the children)
die Männer (the men)

Why is it just repariert and not something like “is repairing” in German?

German usually does not have a separate continuous form like English is repairing.

The simple present tense often covers both:

Der Bauer repariert den Stall.
- can mean: The farmer repairs the barn.
- or: The farmer is repairing the barn. (right now)

Context tells you whether it’s a general fact or a current ongoing action.

What kind of word is während, and does it always make a subordinate clause?

In this sentence, während is a subordinating conjunction meaning while.

As a conjunction, it:

Connects two clauses
Sends the finite verb to the end of its clause

Example:

Der Bauer repariert den Stall, während die Schafe ruhig auf der Wiese stehen.

während can also be a preposition with the genitive, meaning during:

während des Sommers = during the summer

In your sentence, it is clearly a conjunction because it is followed by a full clause (die Schafe … stehen).

Could the word order in the second part be während die Schafe auf der Wiese ruhig stehen instead?

Yes, that is also grammatically correct:

während die Schafe ruhig auf der Wiese stehen
während die Schafe auf der Wiese ruhig stehen

Both are fine. In German, elements inside the clause (adverbs, prepositional phrases, etc.) can usually be reordered for emphasis or style, as long as:

The subordinating conjunction (während) comes first in the clause
The finite verb (stehen) stays at the end

Different orders may sound slightly more natural in different contexts, but both versions are acceptable.

Why is Bauer capitalized?

In German, all nouns are written with a capital letter, regardless of their position in the sentence:

der Bauer (the farmer)
der Stall (the barn)
die Schafe (the sheep)
die Wiese (the meadow)

This is a standard spelling rule in German.

How do I know that Bauer, Stall, and Wiese have the genders der, der, and die?

Unfortunately, grammatical gender in German is largely lexical: you have to learn each noun together with its article.

der Bauer (masculine)
der Stall (masculine)
die Wiese (feminine)
das Schaf (neuter)

Some endings and patterns help (for example, many nouns ending in -e are feminine), but there are many exceptions. A good habit:

Always memorize: article + noun + plural form
- e.g. der Stall, die Ställe; die Wiese, die Wiesen; das Schaf, die Schafe.

Why is it stehen and not just sind in die Schafe … stehen?

sein (sind) just expresses existence or state: to be.
stehen describes the specific position: to stand.

Die Schafe sind auf der Wiese.
= The sheep are on the meadow. (They might be standing, lying, walking, etc.)
Die Schafe stehen auf der Wiese.
= The sheep are standing on the meadow. (Their posture is standing.)

In your sentence, the idea is that the sheep are standing calmly, so stehen is more precise than sind.