Forhjulet på min cykel ser fint ud, men baghjulet er stadig fladt.

Because forhjul and baghjul are neuter nouns. The last part of each compound is hjul (wheel), and hjul is neuter: et hjul.

So:

• et hjul = a wheel
• hjulet = the wheel
• et forhjul = a front wheel
• forhjulet = the front wheel
• et baghjul = a rear wheel
• baghjulet = the rear wheel

The definite singular ending for a neuter noun is often -et.

Because Danish usually writes compound nouns as one word.

So:

• for
  • hjul = forhjul
• bag
  • hjul = baghjul

This is very common in Danish, much more so than in English. Where English often writes front wheel as two words, Danish prefers one compound word.

In Danish, på is very natural when talking about something attached to or belonging as a part of an object.

So forhjulet på min cykel literally looks like the front wheel on my bike, but in English we would often translate it as the front wheel of my bike or just my bike’s front wheel.

Danish often uses this pattern for parts of things:

• døren på bilen = the door of/on the car
• taget på huset = the roof of/on the house

A more compact possessive version is also possible, such as min cykels forhjul, but forhjulet på min cykel sounds very natural and everyday.

Because cykel is a common gender noun, not a neuter noun.

In Danish possessives:

• min is used with common gender singular nouns
• mit is used with neuter singular nouns
• mine is used with plurals

So:

• min cykel = my bike
• mit hjul = my wheel
• mine cykler = my bikes

Since cykel takes en (en cykel), it must also take min.

Because a possessive like min already does the job that an article would normally do.

So Danish says:

• min cykel = my bike

not:

• en min cykel
• den min cykel

This works like English: we say my bike, not the my bike.

Se ud is a fixed verb expression meaning to look or to appear.

So:

• ser fint ud = looks fine

In a main clause, Danish often splits this kind of verb expression:

• Forhjulet ser fint ud.

Here:

• ser is the finite verb
• ud stays later in the sentence

This is similar to how some verb particles behave in English, although the grammar is not exactly the same.

You can think of se ud as one unit whose parts get separated by normal Danish word order.

Because the adjectives agree with neuter singular nouns.

Both forhjulet and baghjulet are neuter singular, so the predicate adjective takes -t:

• fin → fint
• flad → fladt

That is why the sentence has:

• ser fint ud
• er stadig fladt

A quick comparison:

• Cyklen er fin. = The bike is nice.
  
  • cykel is common gender
• Hjulet er fint. = The wheel is nice/fine.
  
  • hjul is neuter

And similarly:

• Dækket er fladt. = The tire is flat.
• Slangen er flad. = The inner tube is flat.

So the ending depends on the gender and number of the noun.

This is about nuance.

• ser fint ud means looks fine
• er fladt means is flat

So the first part is about appearance: the front wheel seems okay.
The second part states an actual condition: the rear wheel is still flat.

That contrast is very natural. It suggests something like:

• the front wheel appears okay
• but the rear wheel still has a real problem

You could say baghjulet ser stadig fladt ud, but that would sound more like you are judging by appearance rather than stating the fact.

Stadig means still.

In baghjulet er stadig fladt, it comes after the finite verb er:

• baghjulet = subject
• er = finite verb
• stadig = adverb
• fladt = adjective

This is normal Danish word order in a main clause.

Compare:

• Han er stadig træt. = He is still tired.
• Det virker stadig mærkeligt. = It still seems strange.

So stadig usually sits in the middle of the clause, not at the very end.

Yes. Danish main clauses usually follow the V2 rule, meaning the finite verb comes in second position.

In the first clause:

• Forhjulet på min cykel = first element
• ser = finite verb in second position
• fint ud = the rest

In the second clause:

• baghjulet = first element
• er = finite verb in second position
• stadig fladt = the rest

The conjunction men joins two main clauses, and each clause keeps normal main-clause word order.

A few things may stand out to an English speaker:

• In hjul, the h is silent.
• The j sounds like English y.
• So hjul begins roughly like y-.
• The vowel is not exactly like a normal English vowel, so yool is only an approximation.

So:

• hjul is approximately yool
• forhjul begins roughly FOR-yool
• baghjul begins roughly BAG-yool

Also, Danish pronunciation is often less phonetic than English learners expect, so it is very normal to need audio to get comfortable with words like these.