Learn Hardcore Dutch: Wij nemen liever de fiets als het spits is rond het metrostation. - We prefer to take the bike when it is rush hour around the metro station.

Wij is the stressed form. You use it when you want to emphasize the subject: Wij nemen liever de fiets (en niet zij).
We is the unstressed form, used in neutral, everyday speech.

In normal conversation, We nemen liever de fiets... is more common. Using Wij puts a bit more emphasis on us as the ones who prefer the bike, or it can sound slightly more formal or careful.

Why is it nemen de fiets? Why not something like rijden de fiets or fietsen?

In Dutch, de fiets nemen literally means to take the bike, and idiomatically it means to go by bike / to go cycling. It’s a very common expression.

Wij nemen de fiets = We go by bike (we choose the bike as our means of transport).
Wij fietsen = We cycle / We go by bike (focusing a bit more on the activity of cycling itself).
Wij rijden de fiets is not idiomatic; you would not normally say this.

So your sentence could also be Wij fietsen liever als het spits is rond het metrostation, with almost the same meaning.

What exactly does liever mean here, and how does it work?

Liever is the comparative form of graag and expresses preference. Roughly:

graag = gladly, with pleasure
liever = rather, prefer
liefst = most preferably

So:

Wij nemen graag de fiets = We like to take the bike.
Wij nemen liever de fiets = We would rather take the bike / We prefer to take the bike (compared to something else, usually understood from context).
Wij nemen het liefst de fiets = We prefer the bike most of all.

In your sentence, liever means that, when it is rush hour around the metro station, the bike is your preferred option instead of, for example, the metro.

Where does liever go in the sentence? Could I put it somewhere else?

In main clauses, adverbs like liever usually stand after the conjugated verb and before the object:

Wij nemen liever de fiets.

Other options are possible but change emphasis or style:

Wij liever nemen de fiets. – incorrect.
Liever nemen wij de fiets. – correct, but liever is fronted for emphasis (sounds a bit more formal or emphatic).
Wij nemen de fiets liever. – possible, but less neutral; it can sound slightly marked in this short sentence.

The most natural version is exactly what you have: Wij nemen liever de fiets...

Why is als used here for when? Could I say wanneer het spits is instead?

Both als and wanneer can translate to when, but they differ slightly in feel:

als is very common in everyday speech for:
- repeated/habitual situations: Als het regent, neem ik de bus.
- conditions: Als je wilt, kun je meegaan.
wanneer can also mean when, but it often sounds:
- more formal, or
- more like asking or specifying a point in time: Wanneer kom je?

In your sentence, it’s a repeated situation (habit), so als is the most natural choice:

Wij nemen liever de fiets als het spits is rond het metrostation.

You can say wanneer het spits is, and it is grammatically correct, but in spoken Dutch als would be more typical here.

Shouldn’t it be de spits instead of het spits?

In standard Dutch, spits in the meaning of rush hour is normally:

de spits (common gender), used in expressions like:
- in de spits
- tijdens de spits
- buiten de spits

There is also the word spitsuur (neuter, het spitsuur), which literally means rush-hour:

als het spitsuur is = when it is (the) rush hour.

So, in very standard Dutch, you would usually say:

Wij nemen liever de fiets als het spitsuur is rond het metrostation. or more idiomatically:
Wij nemen liever de fiets tijdens de spits rond het metrostation.

You do hear het spits in some casual speech, influenced by het spitsuur, but most dictionaries and learners’ materials will present de spits as the normal form.

In als het spits is, is the word order correct? Shouldn’t the verb come at the very end of the subordinate clause?

Yes, als het spits is has correct word order for a subordinate clause:

conjunction: als
subject: het
rest of the predicate: spits
finite verb at the end of that core clause: is

The full sentence has an extra phrase after that:

als het spits is
- rond het metrostation

So the core subordinate clause ends with is. It is quite common in Dutch that heavier or more detailed parts (like rond het metrostation) are placed after the verb, even though we are still logically in the same time/condition frame. Many grammar books first teach the simpler pattern (verb strictly last), and only later mention this kind of extra phrase after the verb.

What is the nuance of rond het metrostation? Could I also say bij het metrostation?

Both are possible, but they have slightly different nuances:

rond het metrostation = around the metro station, suggesting the whole area surrounding it. This fits well with the idea of congestion in a larger zone.
bij het metrostation = at / near the metro station, focusing more on the immediate vicinity or the station as a point.

So:

...als het spits is rond het metrostation – sounds like the rush hour in the broader area around the station.
...als het spits is bij het metrostation – more like: when it is rush hour at the station (maybe at its entrances, platforms, etc.).

Both are grammatically fine; which you choose depends on what you want to emphasize.

Could I also say Wij fietsen liever als het spits is rond het metrostation? Does that change the meaning?

Yes, you can, and it is very natural:

Wij nemen liever de fiets... = We prefer to take the bike (choosing the bike as a means of transport).
Wij fietsen liever... = We prefer to cycle.

In most contexts, these are practically equivalent. Wij fietsen liever talks more directly about the activity of cycling, while Wij nemen liever de fiets talks about choosing the bike as your mode of transport. In everyday speech, Wij fietsen liever might even sound a bit more straightforward.

Why is the present tense nemen used, even though this describes something that happens again and again in the future?

Dutch, like English, often uses the present tense for general truths and habitual actions:

English: We take the bike when it’s rush hour around the metro station.
Dutch: Wij nemen liever de fiets als het spits is rond het metrostation.

This does not refer to a single moment, but to a regular habit whenever that situation occurs. You would not normally use a future tense here in Dutch. The simple present (on both sides of the als-clause) is exactly what you want.