Jeg skifter slangen, hvis dækket stadig er fladt i morgen.

Danish very often uses the present tense for future meaning when the time is clear from the context.

So in Jeg skifter slangen ... i morgen, the word i morgen already tells you this is about the future. Because of that, Danish does not need a separate future form here.

English often does something similar:

• I’m changing the tube tomorrow
• I change it tomorrow (less common, but possible in some contexts)

You could also say Jeg vil skifte slangen, but that often sounds more like I will / I’m willing to / I intend to change the tube, so it can add a sense of intention or decision rather than just a neutral future statement.

Slangen is the definite form of slange.

• en slange = a tube / a snake / a hose
• slangen = the tube / the snake / the hose

In Danish, the definite article is usually added to the end of the noun instead of being a separate word like English the.

Here, slangen means the inner tube, because the speaker is talking about a specific one, probably the one inside the tire.

For the same reason as slangen: dækket is the definite form.

• et dæk = a tire
• dækket = the tire

So the sentence is talking about a specific tire, not just any tire.

Also notice that dæk is a neuter noun (et-word), so its definite ending is -et:

• et dæk
• dækket

Because flad has to agree with the noun it describes.

Here it describes dækket, and dæk is a neuter noun (et dæk). When many adjectives are used predicatively with a neuter singular noun, they take -t:

• Dækket er fladt = The tire is flat
• compare with a common-gender noun: Cyklen er flad would be wrong, because cykel is not something you usually call flat, but grammatically the adjective would stay flad with an en-word.

So:

• en-word: often flad
• et-word: fladt

Because this is a subordinate clause introduced by hvis.

In Danish subordinate clauses, sentence adverbs like stadig, ikke, nok, jo, etc. usually come before the finite verb.

So the normal order is:

• hvis + subject + adverb + verb
• hvis dækket stadig er fladt

Compare that with a main clause, where Danish often puts the finite verb in second position:

• Dækket er stadig fladt

This is a very important word-order pattern in Danish.

Yes. Hvis means if and introduces a condition.

So:

• Jeg skifter slangen, hvis dækket stadig er fladt i morgen means
• I’ll change the tube if the tire is still flat tomorrow

It sets up a condition: first the speaker checks whether the tire is still flat tomorrow, and only then changes the tube.

A useful comparison:

• hvis = if
• når = when (used when something is expected to happen, not just possible)

So hvis is right here because the tire may or may not still be flat tomorrow.

Because standard Danish spelling normally uses a comma before a subordinate clause like one introduced by hvis.

So:

• Jeg skifter slangen, hvis dækket stadig er fladt i morgen.

This comma helps show that hvis dækket stadig er fladt i morgen is a dependent clause.

Danish comma rules can be a bit different from English, so this is something learners often notice.

Yes, it can often move, although the emphasis may change slightly.

Your sentence:

• Jeg skifter slangen, hvis dækket stadig er fladt i morgen.

Also possible:

• Jeg skifter slangen i morgen, hvis dækket stadig er fladt.

The difference is mostly about what i morgen feels closest to.

• ... fladt i morgen focuses on the tire’s condition tomorrow.
• Jeg skifter slangen i morgen ... focuses more on the time of changing the tube.

In real conversation, both can work, but the original version strongly suggests: tomorrow, if the tire is still flat, then I’ll change the tube.

Yes, slange can mean several things depending on context:

• snake
• hose
• tube, especially an inner tube in a bicycle tire

In this sentence, because of dækket and fladt, the context is clearly about a tire, so slangen means the inner tube.

This is very common in Danish: one word can have several meanings, and the situation tells you which one is intended.

Yes, but it would mean something different.

• Jeg skifter slangen = I’m changing the inner tube
• Jeg skifter dækket = I’m changing the tire

So the original sentence specifically says the speaker plans to replace the tube, not the whole tire.

That distinction matters a lot in bike or car contexts.

Yes. Stadig is the normal word for still in the sense of continuing to be.

• Dækket er stadig fladt = The tire is still flat

That is exactly the right choice here.

Just remember that still in English can have different meanings, and Danish may use different words depending on the sense:

• still = continuing → stadig
• still = quiet / motionless → stille

So here it must be stadig, not stille.