Learn Hardcore Hungarian: Minden nap külön, és néha furcsa, amikor sötétben megyek a munkába. - Every day is separate, and sometimes strange, when I go to work in the dark.

minden nap (two words) = every day (focus on each separate day)
mindennap (one word) = every day / daily (more like an adverb: on a daily basis)

In your sentence:

Minden nap külön…
This stresses the individuality of each day: Every day is separate/different.

If you said:

Mindennap külön…
it would sound more like: On a daily basis it’s different…, a bit more general and adverb-like.

Both are grammatically possible, but minden nap külön sounds more natural here, because külön is describing each day as its own separate thing.

There is no van (“is”) in Minden nap külön, és néha furcsa. Is that correct? When can you drop van in Hungarian?

Yes, this is correct and very normal.

In Hungarian, in the present tense, 3rd person singular and plural forms of lenni (van, vannak) are usually omitted in simple statements:

A nap hosszú. = The day (is) long.
Az utcák üresek. = The streets (are) empty.
Minden nap külön. = Every day (is) separate/different.
Néha furcsa. = Sometimes (it is) strange.

The verb van / vannak is typically dropped when:

It’s present tense, and
It’s just linking a subject to a nominal or adjectival predicate (X is Y / X is [adjective]).

You would keep forms of lenni:

in the past or future (e.g. volt, lesz),
in negative sentences like nincs, nincsenek,
or when you want special emphasis or a particular construction.

So your sentence is a normal example of this omission.

What exactly does külön mean in this sentence? Could we say más or különös instead?

Here külön is used as a kind of predicate adjective/adverb meaning something like:

separate, distinct, individual, or
in a more natural translation: different.

So Minden nap külön ≈ Every day is different / Every day is its own thing.

Compare:

külön – separate, individually, apart
külön-külön – each one separately
más – (an)other, different
különös – strange, peculiar (closer to furcsa)

You could say:

Minden nap más. – Very common, literally: Every day is different.
Minden nap különös. – Would mean: Every day is peculiar/strange (that would be about weirdness, not separateness).

So:

To keep the idea that each day is its own separate experience, külön works.
If you simply want “Every day is different”, Minden nap más is more usual and very idiomatic.

Why is there a comma before és, and another comma before amikor?

Hungarian comma rules differ from English, and they’re quite strict.

Comma before és
The first part is essentially a full clause with an omitted van:
- Minden nap külön, és néha furcsa, …
  ⇒ [Every day is different] and [sometimes (it is) strange]
You’re joining two predicate parts about the same “it” (the experience), so Hungarian usually separates them with a comma when they are full, balanced parts.
Comma before amikor
amikor starts a subordinate clause (a when-clause):
- main part: Minden nap külön, és néha furcsa,
- subordinate part: amikor sötétben megyek a munkába.
In Hungarian, a subordinate clause introduced by amikor is almost always preceded by a comma.

A slightly “cleaner” punctuation that many writers would choose:

Minden nap külön, és néha furcsa, amikor sötétben megyek munkába.

You might see slight variations (some people drop the comma before és in more informal writing), but the comma before amikor is standard.

What is the function of amikor here? What is the difference between amikor and mikor?

Here amikor introduces a time clause:

… amikor sötétben megyek a munkába.
= … when I go to work in the dark.

amikor vs mikor:

amikor
- more clearly a subordinating conjunction = when (in a clause)
- neutral, works well in both spoken and written Hungarian
- e.g. Örülök, amikor találkozunk. – I’m happy when we meet.
mikor
- can be a question word (When?) and can also be used as a conjunction in many spoken contexts
- in writing, amikor is often preferred for the conjunction sense, while mikor is more typical in questions:
  - Mikor mész a munkába? – When are you going to work?

In everyday speech, many Hungarians use mikor where amikor would also be acceptable, but amikor is the safer choice in a sentence like yours.

Why is sötétben in the -ban/-ben case? Could you just say sötét?

sötétben is sötét (darkness) + the inessive case ending -ban/-ben, which usually means in something.

So:

sötét = darkness / dark
sötétben = in the dark

Hungarian expresses “in the dark” literally as being in darkness:

sötétben járok az utcán – I walk in the dark in the street.
Sötétben nem látok jól. – I don’t see well in the dark.

You cannot just say sötét, because that is more like the noun or adjective “dark/darkness” on its own, not the expression in the dark. You need the -ban/-ben ending to give the correct meaning.

You can add an article:

a sötétben megyek a munkába – I go to work in the dark.

Omitting the article (sötétben) sounds a bit more general / abstract; including it (a sötétben) sounds more like in that darkness or in the dark conditions. Both are used.

Do I need the article in a munkába? What is the difference between megyek a munkába and munkába megyek?

In everyday Hungarian, the most idiomatic phrase is:

munkába megyek – I’m going to work.

Here:

munka = work
-ba = into / to (illative case)
no article: you’re talking about work in general, like a routine.

So:

Sötétben megyek munkába. – Very natural: I go to work in the dark.

Using the article:

megyek a munkába is grammatically possible, but sounds less idiomatic and a bit clumsy in this everyday sense.
a munkába megyek is better than megyek a munkába, word-order-wise, but you still more often hear munkába megyek (no article) in the “go to work” expression.

In short:

Prefer munkába megyek for “I go to work”.
The version megyek a munkába is understandable but not the most natural phrasing for this fixed everyday idea.

Why is the ending -ba used on munka? Could you use another case like -hoz?

The ending -ba/-be is the illative case, which generally means into or to the inside of something:

házba megyek – I go into the house.
iskolába megyek – I go to school.
munkába megyek – I go to work.

For regular destinations like school, work, cinema, etc., Hungarian often uses this same -ba/-be pattern, even though English just says to.

You could say other things, but the meaning changes:

a munkahelyemre megyek – I’m going to my workplace (more specific)
a munkához megyek – sounds odd; -hoz (allative) is more “towards / to (near)” someone or something, not the standard choice for “to work” as a daily destination.

So for the fixed meaning “go to work (as an activity/place)”, munkába megyek with -ba is the natural form.

Where can néha go in the sentence? Could I say néha megyek sötétben a munkába or furcsa néha?

néha means sometimes, and as an adverb it is fairly flexible in position, but not all positions feel equally natural.

Original:

Minden nap külön, és néha furcsa, amikor sötétben megyek a munkába.

Here néha modifies furcsa: it is sometimes strange.

Other natural positions:

Néha furcsa, amikor sötétben megyek munkába.
Amikor sötétben megyek munkába, néha furcsa.

Your suggested options:

Néha megyek sötétben a munkába.
This means: Sometimes I go to work in the dark (so on some days it’s dark, other days not). That changes the meaning; it no longer says that the feeling is sometimes strange, but that the action itself only sometimes happens in darkness.
furcsa néha
This is understandable, but less natural in this kind of predicate clause. You might say something like Olyan furcsa néha. – It’s so strange sometimes. but usually you put néha before the adjective or at the beginning/near the verb.

So, for your original meaning (“it is sometimes strange when I go to work in the dark”), the neatest versions keep néha close to furcsa:

Néha furcsa, amikor sötétben megyek munkába.
Minden nap külön, és néha furcsa, amikor sötétben megyek munkába.

Could I move the amikor-clause to the front: Amikor sötétben megyek a munkába, minden nap külön, és néha furcsa? Does that change anything?

Yes, you can move the amikor-clause to the beginning:

Amikor sötétben megyek munkába, minden nap külön, és néha furcsa.

This is grammatically correct and quite natural. The difference is mainly in emphasis:

Fronted amikor-clause:
First you set the time situation (“When I go to work in the dark…”) and then you state what is true in that situation (“…every day is different, and sometimes strange.”). This draws more attention to the condition/time.
Original word order:
You first describe the experience (“Every day is different and sometimes strange”) and then clarify in what situation that happens (“when I go to work in the dark”).

Both are fine; Hungarian allows this kind of reordering quite freely, and the commas are important to show where the clauses begin and end.

Is the whole sentence natural Hungarian? Are there any more common ways to say the same thing?

The sentence is grammatically fine, but you might make small adjustments for more typical everyday style.

Original:

Minden nap külön, és néha furcsa, amikor sötétben megyek a munkába.

More idiomatic variants a native might use:

Use más instead of külön, and drop the article before munkába:
- Minden nap más, és néha furcsa, amikor sötétben megyek munkába.
Or reorder a bit:
- Amikor sötétben megyek munkába, minden nap más, és néha furcsa.
Or simplify the structure:
- Minden nap más, és néha furcsának érzem, hogy sötétben megyek munkába.
  (Every day is different, and sometimes I feel it’s strange that I go to work in the dark.)

Your version is understandable and correct; a teacher might just suggest:

…megyek munkába instead of …megyek a munkába, and
possibly Minden nap más instead of Minden nap külön, depending on the exact nuance you want.