Learn Hardcore German: Im Stall riechen die Kühe stark, aber nur der alte Eimer stinkt wirklich schlimm. - In the stable the cows smell strongly, but only the old bucket really stinks badly.

riechen = to smell (neutral). It just says that something has a smell; whether it’s good or bad depends on context or extra words:
- Die Blumen riechen gut. – The flowers smell good.
- Die Kühe riechen stark. – The cows smell strongly (noticeably), but this doesn’t automatically mean “disgusting”; it can just mean “they have a strong barn/cow smell.”
stinken = to stink (always negative). It means “to smell bad / to reek”:
- Der alte Eimer stinkt wirklich schlimm. – The old bucket really stinks (very badly).

So the sentence contrasts:

Cows: neutral/strong smell → riechen stark
Bucket: clearly bad smell → stinkt wirklich schlimm

Why is it Im Stall and not In dem Stall?

Im is simply the contracted form of in dem:

in (preposition) + dem (dative masculine/neuter article) → im

So:

Im Stall = in dem Stall = in the barn / in the stable

This kind of contraction is very common and usually preferred in spoken and written German when possible:

am = an + dem
beim = bei + dem
zum = zu + dem
ins = in + das

You could say In dem Stall riechen die Kühe stark, but Im Stall sounds more natural and is what you normally hear.

Why is Stall in the dative case here?

Because of the preposition in and the meaning:

in can take dative (location) or accusative (movement).

Basic rule:

Wo? (Where? – location, no movement) → dative
- im Stall (in the barn)
Wohin? (Where to? – movement into) → accusative
- in den Stall gehen (go into the barn)

In your sentence, the cows and the bucket are located in the barn; nobody is moving into it. That’s why in + dem (Stall) uses the dative, and then contracts to im Stall.

Could I also say Die Kühe riechen im Stall stark? What changes if I do?

Yes, that sentence is grammatically correct too:

Die Kühe riechen im Stall stark.

The difference is mainly in emphasis and sentence rhythm.

German main clauses generally have:

Position 1: one element (subject, adverbial, object, etc.)
Position 2: the conjugated verb

Your original sentence:

Im Stall (position 1) riechen (2) die Kühe stark (rest)

Starting with Im Stall emphasizes the location or sets the scene: In the barn, the cows smell strongly…

If you start with the subject:

Die Kühe (1) riechen (2) im Stall stark (rest)

This is more neutral and just states something about “the cows” without highlighting the place as strongly.

Both versions are correct; the choice is stylistic and about what you want to foreground: location vs. subject.

Why is it die Kühe but der alte Eimer?

Two different things are happening here: gender and number.

Gender & number of the nouns
- die Kuh = the cow (singular, feminine)
- die Kühe = the cows (plural)
- der Eimer = the bucket (singular, masculine)
Case in the sentence
Both die Kühe and der alte Eimer are subjects, so they are in the nominative case.

Nominative forms:

Feminine singular: die Kuh
Plural (all genders): die Kühe
Masculine singular: der Eimer

So:

die Kühe – nominative plural subject
der alte Eimer – nominative singular masculine subject

Why is the adjective alte and not alter or alten in der alte Eimer?

Adjective endings in German depend on:

The article type (definite, indefinite, no article)
The case (nominative, accusative, etc.)
The gender/number of the noun

Here we have:

Article: der → definite article
Case: nominative (subject)
Gender/number: masculine singular (der Eimer)

For a definite article + adjective + noun in the nominative masculine singular, the adjective takes -e:

der alte Eimer – the old bucket
der kleine Hund – the small dog
der rote Ball – the red ball

If it were, for example:

Accusative masculine with definite article: den alten Eimer
Dative masculine with definite article: dem alten Eimer

So der alte Eimer is exactly the regular nominative masculine pattern.

Why do we use aber and not sondern here?

Both aber and sondern can be translated as “but”, but they are used in different situations.

aber = “but” to express contrast, without directly correcting a negation
sondern = “but rather / but instead” to correct something after a negation (nicht / kein)

Examples:

Ich mag Kühe, aber ich mag Schweine nicht.
I like cows, but I don’t like pigs. (contrast ⇒ aber)
Ich mag keine Kühe, sondern Schweine.
I don’t like cows, but (instead) pigs. (negation + correction ⇒ sondern)

Your sentence:

Im Stall riechen die Kühe stark, aber nur der alte Eimer stinkt wirklich schlimm.

Nothing is being denied and then corrected. We just have a contrast:

Cows smell strongly.
But only the old bucket really stinks badly.

So aber is the correct conjunction here.

What exactly does nur do in aber nur der alte Eimer stinkt wirklich schlimm?

nur means “only” and it limits what part of the statement is true.

In this sentence:

aber nur der alte Eimer stinkt wirklich schlimm

nur directly limits der alte Eimer:

Not everything in the barn stinks terribly.
Only the old bucket does.

Slightly different emphases if you move nur:

Nur der alte Eimer stinkt wirklich schlimm.
Only the old bucket really stinks badly. (standard, subject is limited)

Other positions could change the meaning:

Der alte Eimer stinkt nur wirklich schlimm.
Almost sounds like: The old bucket only stinks really badly (and doesn’t do anything else) – a different, odd emphasis.

So in your sentence, nur belongs directly before der alte Eimer and focuses the limitation on the subject.

What is the difference between stark and schlimm here?

They describe different aspects of the smell:

stark = strong / intense
It tells you about the intensity of a smell (loudness, so to speak), but not necessarily whether it’s good or bad.
- Es riecht stark nach Kühen. – It smells strongly of cows.
- Das Parfüm riecht stark. – The perfume has a strong smell.
schlimm = bad / terrible
It describes how unpleasant or bad something is. When used with stinken, it reinforces how awful the smell is.
- Der Gestank ist schlimm. – The stench is bad / awful.

In the sentence:

die Kühe riechen stark – The cows smell strongly (intense smell, barn/cow smell).
stinkt wirklich schlimm – really stinks badly (it’s not just strong, it’s disgusting).

So stark = strength of the smell, schlimm = how unpleasant it is.

Could I say stinkt wirklich schlecht instead of stinkt wirklich schlimm?

You could say stinkt wirklich schlecht, and it would be understood, but it’s less idiomatic.

Typical combinations:

gut / schlecht riechen – smell good / bad
- Die Suppe riecht schlecht. – The soup smells bad.
stinken is already negative, so Germans often strengthen it with:
- stinkt furchtbar – stinks terribly
- stinkt schrecklich – stinks horribly
- stinkt wirklich schlimm – really stinks badly

schlimm here sounds more natural with stinken than schlecht.
So:

… stinkt wirklich schlimm. – very idiomatic
… stinkt wirklich schlecht. – understandable, but not the usual collocation.

How would I say “In the barn, it smells strongly of cows” in German?

A very natural way would be to use es riecht nach …:

Im Stall riecht es stark nach Kühen.

Breakdown:

Im Stall – in the barn (location, dative)
riecht – smells (3rd person singular)
es – dummy subject (it) required in German
stark – strongly
nach Kühen – of cows (literally “after cows”; nach + dative for “smells like/of”)

So, instead of making the cows the grammatical subject, German often uses:

Es riecht nach X. – It smells of X.

Are riechen and stinken transitive verbs? Can I say Ich rieche die Kühe?

They are usually intransitive when describing how something smells:

Die Kühe riechen stark. – The cows smell strongly.
Der Eimer stinkt. – The bucket stinks.

There is a second, different use of riechen that can be transitive:

To smell something intentionally (to sniff)
- Ich rieche die Blumen. – I smell the flowers (I deliberately sniff them).
To smell like / of something – intransitive with nach + Dativ
- Es riecht nach Kühen. – It smells of cows.
- Der Eimer stinkt nach faulen Eiern. – The bucket stinks of rotten eggs.

In your sentence:

Die Kühe riechen stark. – intransitive, describing their own smell
Der alte Eimer stinkt … – intransitive, describes that the bucket itself gives off a bad smell.

Ich rieche die Kühe would mean “I am (deliberately) smelling the cows,” which is possible but a bit unusual in everyday context; it shifts the meaning from “they smell (have an odor)” to “I sniff them.”

Why is wirklich placed before schlimm in stinkt wirklich schlimm?

wirklich here functions like “really / truly” and intensifies schlimm:

schlimm – bad / awful
wirklich schlimm – really bad / truly awful

Word order rules for adverbs and adjectives in such combinations:

Degree/attitude adverbs (sehr, ziemlich, total, wirklich, unglaublich) usually come before the adjective or adverb they modify:
- wirklich schlimm – really bad
- sehr stark – very strong
- ziemlich gut – pretty good

So:

stinkt wirklich schlimm = “stinks really badly”

Putting wirklich elsewhere would change the nuance:

wirklich stinkt schlimm – sounds wrong/unnatural
stinkt schlimm wirklich – very odd, not idiomatic

The normal and correct way is: stinkt wirklich schlimm.