Na de rotonde gaat het fietspad door een scherpe bocht, dus daar fiets ik altijd langzamer.

Because Dutch main clauses follow the V2 rule: the finite verb must come in the second position.

Here, Na de rotonde is placed first. That means the verb gaat has to come next:

• Na de rotonde gaat het fietspad...

If you started with the subject, you would get:

• Het fietspad gaat na de rotonde...

Both are grammatical, but the original sentence emphasizes what happens after the roundabout.

Usually, na is the correct choice here.

• na de rotonde = after the roundabout, in the sequence of the route
• achter de rotonde = behind the roundabout, referring more to physical position

In road directions, Dutch normally uses na when one thing comes next along the route.

Because rotonde is a de-word in Dutch.

So you say:

• de rotonde
• na de rotonde

This is something learners usually have to memorize noun by noun.

Right. Here gaan is not about the path physically moving. In Dutch, roads, paths, and routes can gaan somewhere, meaning:

• go
• run
• continue
• lead

So het fietspad gaat door een scherpe bocht means that the bike path runs through / takes a sharp bend.

This is a very normal use of gaan in Dutch.

Because fietspad is a het-word.

So:

• het fietspad
• een fietspad

Also, Dutch often combines nouns into one compound word, so:

• fiets
  • pad = fietspad

English often writes these separately or with a space, but Dutch usually writes them as one word.

In this sentence, door is used in the sense of through or around a bend.

So:

• door een bocht gaan = to go through a curve / to bend around a curve

This is idiomatic Dutch for the shape or direction of a road or path.

It sounds natural with roads, paths, and routes.

Because the sentence is describing the kind of bend it is, not identifying a previously known specific bend.

• een scherpe bocht = a sharp bend
• de scherpe bocht = the sharp bend

If speaker and listener already both knew exactly which bend was meant, de could be possible. But here een is the normal choice.

Yes. Scherp literally means sharp, and with roads or bends:

• een scherpe bocht = a sharp bend / a tight curve

Because bocht is a de-word, the adjective takes -e:

• de bocht
• een scherpe bocht

So this is also a good example of Dutch adjective ending rules.

Because daar has been moved to the front for emphasis, and Dutch still keeps the verb in second position.

So:

• neutral order: Ik fiets daar altijd langzamer
• fronted for emphasis: Daar fiets ik altijd langzamer

Once daar is first, the verb fiets must come next, before the subject ik.

That is another example of the V2 rule.

Here daar means there, referring back to the place just mentioned: the spot where the bike path goes through that sharp bend.

So it is not introducing new information. It points back to the location already described.

In English, you might naturally say:

• so I always cycle more slowly there

That is exactly the function of daar here.

Because in Dutch, fietsen means to cycle / to ride a bike.

So:

• ik fiets = I cycle / I ride my bike

Dutch usually uses fietsen specifically for bicycle movement.
Rijden is broader and can be used for driving or riding in general, but fietsen is the most natural verb here.

Dus means so or therefore. It connects the second clause to the first.

The important thing is that the clause after dus is still a main clause, so normal main-clause word order applies.

The clause itself is:

• daar fiets ik altijd langzamer

Here daar is first, so the verb fiets comes second.

So dus does not create subordinate-clause word order. It does not send the verb to the end.

Compare:

• ..., dus daar fiets ik altijd langzamer.
• ..., omdat het daar gevaarlijk is.

After omdat, the verb goes to the end; after dus, it does not.

Langzamer is a comparative adverb here, meaning more slowly.

Dutch, like English, can leave the comparison implicit if it is obvious:

• Ik fiets daar langzamer. = I cycle more slowly there.

The sentence does not need to say than elsewhere or than usual if that is understood from context.

You could make it more explicit, for example:

• Daar fiets ik altijd langzamer dan op een recht stuk.

But the original sentence is perfectly natural without that.

Langzamer is the normal comparative form of langzaam:

• langzaam = slow / slowly
• langzamer = slower / more slowly

In this sentence it functions adverbially, modifying fiets.

Dutch can also say:

• Ik fiets daar minder snel.

That also means I cycle less fast / more slowly there.

Both are natural, but langzamer is very straightforward and common.

Because altijd is a frequency adverb (always), while langzamer describes how the action happens.

A very natural Dutch order is:

• place/time element
• verb + subject
• frequency adverb
• manner adverb

So:

• Daar fiets ik altijd langzamer

This sounds natural and clear:

• daar = where
• fiets ik = action + subject
• altijd = how often
• langzamer = how

It is one sentence made up of two main clauses joined by dus:

1. Na de rotonde gaat het fietspad door een scherpe bocht
2. dus daar fiets ik altijd langzamer

Each part could stand on its own as a full sentence.
They are linked because the second clause is the result of the first.

Yes, that is also possible and quite natural.

Compare:

• Het fietspad gaat door een scherpe bocht
• Het fietspad maakt een scherpe bocht

Both can describe the path bending sharply.

The original version slightly emphasizes the path’s course through the bend, while maakt een scherpe bocht directly says it makes a sharp turn. In everyday Dutch, both work well.