Hun tager sådan nogle solbriller på, når solen er stærk.

Because tage ... på is a very common Danish verb-particle combination meaning to put on or, in some contexts, to wear.

In a main clause, Danish often splits these up:

• Hun tager solbriller på.

But in the infinitive, they stay together:

• at tage solbriller på

So this works a lot like a separable phrasal verb.

Sådan nogle is a conversational way to mean something like:

• some ... like that
• that kind of ...
• those sort of ...

So sådan nogle solbriller suggests a type of sunglasses rather than identifying a specific pair.

It adds an informal, slightly vague tone. The sentence would still work without it:

• Hun tager solbriller på, når solen er stærk.

That version is simpler and more neutral.

In Danish, solbriller is normally plural, just like sunglasses in English.

So even one pair is usually expressed with a plural noun:

• solbriller = sunglasses
• et par solbriller = a pair of sunglasses

That is completely normal Danish usage.

Because når is used for something that happens whenever or when a situation occurs regularly.

Here the meaning is general or habitual:

• Hun tager ... på, når solen er stærk.
• She does this whenever the sun is strong.

Hvis would sound more like a condition:

• Hvis solen er stærk ... = if the sun is strong ...

So når is the better choice when talking about a repeated habit.

Because når solen er stærk is a subordinate clause, and Danish subordinate clauses do not use the normal main-clause verb-second pattern.

In a main clause, you get:

• Solen er stærk.

But after a subordinating word like når, the order is simply:

• når + subject + verb
• når solen er stærk

So this is standard subordinate-clause word order.

That is a natural Danish way to express the idea that the sun is intense, powerful, or bright.

So solen er stærk means something like:

• the sun is strong
• the sun is intense
• it is very sunny / the sunlight is strong

It may sound a little different from the most common English phrasing, but in Danish it is idiomatic and normal.

Literally, tage ... på means put on.

So:

• Hun tager solbriller på = She puts on sunglasses.

However, with a general statement like this, English may sometimes translate it more naturally as wears:

• She wears sunglasses when the sun is strong.

If you specifically want to say that she already has them on, Danish usually uses:

• Hun har solbriller på. = She is wearing sunglasses.

So:

• tage ... på = put on
• have ... på = have on / be wearing

No, not at all.

The sentence without it is perfectly correct:

• Hun tager solbriller på, når solen er stærk.

Adding sådan nogle makes it more casual and slightly more descriptive, as if the speaker is pointing to a kind of sunglasses or talking loosely about that sort of thing.

So it is a nuance choice, not a grammar requirement.

Because stærk is agreeing with solen, and sol is a common-gender noun in Danish.

With predicative adjectives after er, Danish still shows agreement:

• common gender singular: stærk
• neuter singular: stærkt
• plural: stærke

So:

• solen er stærk = the sun is strong
• lyset er stærkt = the light is strong
• strålerne er stærke = the rays are strong

That is why stærk is correct here.

Yes:

• Når solen er stærk, tager hun sådan nogle solbriller på.

That is completely correct.

The important thing is that in the main clause after the fronted når clause, Danish uses inversion:

• tager hun
• not hun tager

So:

• Hun tager ... på, når solen er stærk.
• Når solen er stærk, tager hun ... på.

Both are good; they just differ in emphasis.

It is talking about a habit or usual behavior.

Danish present tense often covers both:

• what is happening now
• what usually happens
• scheduled or general facts

Here, because of når solen er stærk, the meaning is clearly habitual:

• whenever the sun is strong, she puts on sunglasses

So it is not necessarily describing one specific moment.

Yes. Both are possible.

• Hun tager solbriller på ... = She puts on sunglasses ...
• Hun tager et par solbriller på ... = She puts on a pair of sunglasses ...

Using et par makes the pair idea more explicit, but it is often unnecessary because solbriller already naturally refers to sunglasses as a paired item.