Her ne kadar reji değişmiş olsa da doğaçlama doğal kaldı.

It means although / even though.

So:

• Her ne kadar reji değişmiş olsa da = Although the direction had changed
• doğaçlama doğal kaldı = the improvisation remained natural

This pattern sets up a contrast: one thing changed, but another important quality stayed the same.

In Turkish, these often work together as a matched pair to express concession:

• her ne kadar ...
• ... -sa da / olsa da

Together, they mean something like although ... still ...

So the sentence has this structure:

• Her ne kadar = however much / although
• değişmiş olsa da = even though it had changed

In everyday Turkish, people sometimes use only part of the pattern, but using both sounds complete and natural, especially in more careful or written language.

Also, the da here is not the separate word meaning also. In this structure, it helps create the meaning even though / although.

It is a concessive clause built from:

• değiş- = change
• -miş = a past/completed marker
• olsa = if it were / even if it were from olmak
• da = gives the concessive sense here

So değişmiş olsa da is roughly:

• even though it had changed
• although it may have changed
• literally, something like even if it had changed

In natural English, you usually would not translate each piece separately. You just translate the whole thing as although it had changed or even though it had changed.

Great question, because -miş often confuses learners.

By itself, -miş can suggest:

• reported information
• inference
• a completed state/result

But in structures like değişmiş olsa da, it often feels less like apparently and more like a way to show that the change is already completed before the main statement.

So here:

• değişti = it changed
• değişmiş = it had changed / it has changed / it was in a changed state

In this sentence, değişmiş olsa da sounds more natural and polished than değiştiyse de for this kind of meaning.

Reji is a loanword used especially in theater, cinema, and television. It usually refers to:

• direction
• staging
• the directing
• sometimes the production direction

So in this sentence, reji değişmiş means something like:

• the direction had changed
• the staging had changed
• the director’s approach had changed

The best English translation depends on context.

Here, it is most naturally understood as a noun:

• doğaçlama = improvisation / improvised performance

So:

• doğaçlama doğal kaldı = the improvisation remained natural

In other contexts, doğaçlama can also function more adjectivally, meaning improvised, as in an improvised speech or scene. But in this sentence, it behaves like the subject of the main clause.

Because kalmak means to remain / to stay.

So:

• doğal kaldı = remained natural / stayed natural
• doğaldı = was natural
• doğal oldu = became natural

These are not the same.

The sentence is emphasizing continuity despite change:

• the direction changed,
• but the improvisation still stayed natural.

That is why kaldı is the best choice here.

Because Turkish normally puts the verb at the end of its clause.

So the sentence breaks down like this:

• Her ne kadar reji değişmiş olsa da
  concessive clause, with the verb-like form at the end
• doğaçlama doğal kaldı
  main clause, with the verb kaldı at the end

This is very normal Turkish word order.

English speakers often expect the verb earlier, but in Turkish, waiting until the end of the clause is standard.

Yes. A common alternative would be:

• Reji değişmesine rağmen doğaçlama doğal kaldı.

This also means:

• Although the direction had changed, the improvisation remained natural.

The difference is mostly stylistic:

• her ne kadar ... olsa da sounds a bit more formal or literary
• -mesine rağmen is also common and clear
• ama could also be used in a simpler sentence, such as
  Reji değişti ama doğaçlama doğal kaldı.

That last version is more straightforward, but slightly less elegant than the original.

Yes: the whole contrast pattern is very idiomatic and worth learning as a chunk.

A useful model is:

• Her ne kadar X olsa da, Y.
• Although X, Y.

And in this sentence:

• X = reji değişmiş
• Y = doğaçlama doğal kaldı

So you can reuse the same pattern in many sentences, for example:

• Her ne kadar zor olsa da, deneyeceğim.
  Although it is difficult, I will try.
• Her ne kadar geç kalmış olsa da, toplantıya katıldı.
  Although he was late, he joined the meeting.

This makes the original sentence a very good model for expressing contrast in Turkish.