Üyelik ücretsiz olsa da bazı atölyeler ücretli.

Olsa da is a very common Turkish pattern meaning although, even though, or sometimes even if.

Here, ücretsiz olsa da means something like:

• although it is free
• even though it is free

So the sentence sets up a contrast:

• Üyelik ücretsiz olsa da... = Although membership is free...
• ...bazı atölyeler ücretli. = ...some workshops cost money.

Because ücretsiz is just an adjective meaning free / without charge, and Turkish often uses a form of olmak to build this kind of concessive clause.

• olsa = conditional form of olmak
• olsa da = even if it is / although it is

So:

• ücretsiz = free
• ücretsiz olsa da = although it is free

This is a very natural structure in Turkish. You may also see similar patterns with other adjectives and nouns:

• Zor olsa da... = Although it is difficult...
• Pahalı olsa da... = Although it is expensive...

Because Turkish often leaves out the equivalent of is / are in present-tense sentences, especially in the 3rd person.

So:

• Bazı atölyeler ücretli. literally looks like Some workshops paid/with-fee
• but it means Some workshops are paid / require a fee

This is completely normal Turkish.

If you want a more formal or emphatic version, Turkish can add -dir:

• Bazı atölyeler ücretlidir.

But in everyday language, the shorter version is much more common.

Because this da is a separate particle, not a suffix.

In olsa da, the da is part of the concessive meaning:

• olsa da = although / even though

That is why it is written separately.

This is different from the locative suffix -da / -de, which is attached to the word:

• evde = in the house
• okulda = at school

So:

• olsa da = separate particle
• okulda = attached suffix

They are opposites built from the noun ücret, which means fee or charge.

• ücret = fee
• ücretli = with a fee, paid, not free
• ücretsiz = without a fee, free of charge

The endings are useful to recognize:

• -li often means with / having
• -siz often means without / lacking

So:

• ücretli atölye = a paid workshop
• ücretsiz üyelik = free membership

Because bazı and bazıları do different jobs.

• bazı = some and directly modifies a noun
• bazıları = some of them / some ones, and stands on its own like a pronoun

So:

• bazı atölyeler = some workshops
• bazıları ücretli = some of them are paid

But bazıları atölyeler is not correct in this context.

Because standard Turkish normally uses a plural noun after bazı when it means some.

So:

• bazı atölyeler = some workshops

This matches what an English speaker would expect semantically, even though Turkish handles number differently in some other contexts.

Because Turkish adjectives do not agree with the noun in number the way they do in some languages.

So even though atölyeler is plural, the adjective stays the same:

• atölye ücretli = the workshop is paid
• atölyeler ücretli = the workshops are paid

The adjective ücretli does not need a plural ending.

Yes, you could say something similar with ama:

• Üyelik ücretsiz ama bazı atölyeler ücretli.

This is very natural and common in speech.

The difference is mainly in structure and tone:

• olsa da creates a more tightly linked contrast: although / even though
• ama is a simple coordinating but

So both work, but olsa da sounds a little more like despite that fact...

No, Turkish word order is flexible, but the current order is very natural.

• Üyelik ücretsiz olsa da bazı atölyeler ücretli.

This puts the concessive part first and the main point after it. That is a common pattern in Turkish.

You will also often see a comma in writing:

• Üyelik ücretsiz olsa da, bazı atölyeler ücretli.

The meaning stays the same.

Not exactly. In this kind of sentence, ücretli usually means:

• for a fee
• not free
• fee-based

So bazı atölyeler ücretli is better understood as:

• some workshops require payment
• some workshops are not free

A very literal English translation with paid workshops can sound slightly odd, because in English paid can also suggest that someone is receiving money. Here the Turkish meaning is clearly you have to pay for them.