Min søster siger, at bremsen føles svag, så vi må ikke køre videre.

Because søster is a common-gender singular noun in Danish.

• min = my, used with common gender singular
• mit = my, used with neuter singular
• mine = my, used with plural

So:

• min søster = my sister
• mit hus = my house
• mine søstre = my sisters

In Danish, possessives like min, din, hans, vores usually replace the article.

So Danish says:

• min søster = my sister

not:

• min en søster

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

Here at means that and introduces a subordinate clause.

• Min søster siger = My sister says
• at bremsen føles svag = that the brake feels weak

So at links the two parts together.

In English, that is often optional:

• My sister says the brake feels weak.

In Danish, at is very commonly used in this kind of sentence, especially in careful standard written language.

Bremsen is the definite form of bremse.

• en bremse = a brake
• bremsen = the brake

Danish often adds the definite article to the end of the noun:

• bil → bilen
• dør → døren
• bremse → bremsen

So bremsen literally means the brake.

Good question. Danish can use the singular to refer to the braking system as a whole, especially in everyday speech.

So bremsen føles svag can mean something like:

• the brake feels weak
• or more naturally in English, the brakes feel weak

This is not unusual across languages: sometimes Danish uses a singular noun where English prefers a plural or a more general system-word.

Føles means feels or feels like in the sense of seems by sensation/impression.

• bremsen føles svag = the brake feels weak

It is the -s form of føle used in a passive-like or middle meaning. In practice, learners often just remember føles as feel/seem to feel in sentences like this.

Compare:

• Jeg føler noget. = I feel something.
• Det føles rigtigt. = It feels right.
• Bremsen føles svag. = The brake feels weak.

Because bremsen is a common-gender singular noun, and after verbs like være, blive, virke, føles, the adjective agrees with the noun.

• common gender singular: svag
• neuter singular: svagt
• plural / definite contexts: often svage

Examples:

• En motor er stærk.
• Et signal er stærkt.
• Bremsen føles svag.
• Hjulet virker løst.

Since bremsen is common gender, svag is the correct form.

Here så means so in the sense of therefore / as a result.

• Min søster siger, at bremsen føles svag, så vi må ikke køre videre.
• My sister says that the brake feels weak, so we must not continue driving.

It connects the cause and result:

• brake feels weak → therefore we should not continue

In Danish, må ikke usually expresses prohibition: must not / are not allowed to.

So:

• vi må ikke køre videre = we must not continue driving / we are not allowed to drive on

This can look tricky for English speakers because may not in English can sometimes mean either:

• prohibition: You may not leave
• possibility: It may not work

Danish må ikke here is clearly about not being allowed / not being permitted.

Because må is a modal verb, and modal verbs in Danish are followed directly by the infinitive.

So:

• vi må køre
• vi kan køre
• vi skal køre
• vi vil køre

not:

• vi må at køre

This is similar to English:

• we must drive not
• we must to drive

Videre means further / on / onward.

So:

• køre = drive
• køre videre = keep driving / continue driving / drive on

It adds the idea of continuing rather than just driving in general.

Compare:

• Vi kører. = We are driving.
• Vi kører videre. = We continue driving / drive on.

Yes. After at, Danish uses subordinate clause word order, which does not have the normal main-clause inversion pattern.

Here we get:

• at bremsen føles svag

with the subject bremsen directly before the verb føles.

That is the normal order for a subordinate clause.

Compare a main clause:

• Bremsen føles svag.

Subordinate clause:

• ... at bremsen føles svag.

In this particular sentence, the order happens to look the same, but it is still functioning as a subordinate clause introduced by at.

The commas separate the different clause parts:

• Min søster siger, at bremsen føles svag, så vi må ikke køre videre.

They help show the structure:

1. Min søster siger
2. at bremsen føles svag
3. så vi må ikke køre videre

In Danish, commas are often used around subordinate and connected clauses more visibly than in informal English writing. Even if comma style can vary somewhat depending on the system taught, the commas here help make the sentence easy to read.