På grund af en omvej må vi køre langsommere, selv om fartgrænsen er højere på den anden vej.

A very literal version would be:

Because of a detour must we drive more slowly, even though the speed limit is higher on the other road.

That sounds odd in English, but it helps show two important Danish patterns:

• the main clause uses V2 word order: må vi
• the clause after selv om has normal subordinate-clause order: fartgrænsen er

Yes. På grund af is a fixed expression meaning because of.

So:

• på grund af en omvej = because of a detour

You should learn it as a chunk. After på grund af, you normally get a noun phrase, not a full clause.

Compare:

• på grund af en omvej = because of a detour
• fordi der er en omvej = because there is a detour

Both can be correct, but the grammar is different.

Because Danish main clauses follow the V2 rule: the finite verb normally comes in the second position.

Here, the sentence starts with the adverbial phrase:

På grund af en omvej

Once that takes the first position, the verb must come next:

• På grund af en omvej må vi køre langsommere

If the sentence started directly with the subject, you would get:

• Vi må køre langsommere på grund af en omvej

Both are possible, but the original emphasizes the reason first.

Here må means must / have to.

Danish må can sometimes correspond to English may, but in this sentence the context shows necessity, not permission.

So:

• vi må køre langsommere = we have to drive more slowly

It sounds like circumstances force it, not that someone is giving permission.

Because omvej is a common-gender noun, so its indefinite singular article is en.

• en omvej = a detour
• omvejen = the detour

Also, omvej is a compound noun:

• om = around
• vej = road / way

So the basic idea is a road or route that goes around something.

Because the sentence is making a comparison.

• langsomt = slowly
• langsommere = more slowly / slower

The idea is not just we drive slowly, but we drive more slowly than we otherwise would.

In Danish, the comparative form is often made with -ere:

• langsom → langsommere
• høj → højere

Here langsommere functions adverbially because it describes how we drive.

Because it describes the manner of the action:

• køre langsommere = drive more slowly

This is normal Danish word order. The verb comes first in the verbal part, and the adverbial complement follows it.

You can think of it as parallel to English:

• drive more slowly

Here selv om means even though / although.

It introduces a contrast:

• we have to drive more slowly
• even though the speed limit is higher on the other road

So the sentence says that, despite the higher speed limit elsewhere, the detour still makes them go slower.

You will also often see selvom in Danish. In this sentence, selv om is functioning as that same kind of contrastive conjunction.

Because selv om introduces a subordinate clause, and subordinate clauses do not use main-clause V2 word order.

So you get normal subject-verb order:

• selv om fartgrænsen er højere

Compare:

• main clause: Fartgrænsen er højere
• subordinate clause: selv om fartgrænsen er højere

In both cases here, the subject comes before the verb.

Fartgrænsen is a compound noun plus the definite ending.

It breaks down as:

• fart = speed
• grænse = limit / boundary
• -n = the definite ending

So:

• fartgrænse = speed limit
• fartgrænsen = the speed limit

This is very typical Danish: instead of several separate words, Danish often builds one compound noun.

Because Danish uses higher/lower with limits, numbers, prices, temperatures, and similar things, just like English often does.

So:

• fartgrænsen er højere = the speed limit is higher

This does not mean physically high. It means the permitted speed is greater.

Because vej is a common-gender noun.

Common-gender nouns take:

• den in the definite form
• anden in this pattern

So:

• den anden vej = the other road

If the noun were neuter, you would expect:

• det andet ...

Also, anden here usually means other, not necessarily second in a strict counting sense.

It means on the other road.

The preposition på is used naturally with roads in many cases in Danish:

• på vejen = on the road
• på den anden vej = on the other road

So the sentence contrasts the detour route with another road where the speed limit is higher.

Yes, it is normal and helpful because selv om introduces a subordinate clause.

So the comma separates:

• the main clause: På grund af en omvej må vi køre langsommere
• the subordinate clause: selv om fartgrænsen er højere på den anden vej

In real Danish writing, comma practice can vary somewhat depending on the comma system being used, but this comma is completely natural.