When I was watching TV, a Finnish woman living in Japan said that, “I think Japanese parfaits have evolved in a unique way and they are like arts.” ¶
She said that she had eaten 2,000 types of parfait in 10 years.

"While I was watching TV" is another way you could write the first phrase.

Actually, I think parfaits are delicious,; however, I didn’t think it wasthey were unique to Japan.

Actually,lthough I think parfaits are delicious, however I didn’t think it wasthat they were unique to Japan.

When I was watching TV, a Finnish woman living in Japan said that, “I think Japanese parfaits have evolved in a unique way and they are like works of arts.” ¶
She said that she had eaten 2,000 types of parfait in 10 years.

Actually, I also think parfaits are delicious, howeverbut I didn’t think the variety of parfaits was unique to Japan.

I think there are also in France and so onought they were also popular in France and other countries.

When I was watching TV, a Finnish woman living in Japan said that, “I think Japanese parfaits have evolved in a unique way and they are like arts.” ¶
She said that she had eaten 2,000 types of parfait in 10 years.

you would use "art" instead of "arts" here. "art" even though it doesn't have an 's' at the end, can still be plural

I think they're are also in France and so on.

I think there are also parfaits in France and so on.

When I was watching TV, I hear a Finnish woman living in Japan said that, “I think , “Japanese parfaits have evolved in a unique way and they are like artworks.” ¶
She saimentioned that she had eaten 2,000countless types of parfait in 10 yearsover the last decade.

Actually,CLEARER: I think parfaits are delicious, however I didn’t think it wasbut don't think they are unique to Japan.

GRAMMAR: The plural "they" is better than the singular "it."

I think there are also in France and so onThey are also popular in many European countries.

WhenThe other day I was watching TV, and a Finnish woman living in Japan came on and said that, “I think Japanese parfaits have evolved in a unique way and they are like an arts.” ¶
She said that she had eaten 2,000 types of parfait in 10 years.

Using "when I was..." Would shine too much of a spotlight on what otherwise is just a background setting,
”テレビ見てた時、”みたいな表現になってしまいます

Actually,While I think parfaits are delicious, however I didn’t think it was unique to Japan.

Actually is closer to 実は while 確かに is more like indeed.

I think therey are also in France and so on.

Or you can say, I think there are also parfaits in France ...

When I was watching TV, a Finnish woman living in Japan said that, “I think Japanese parfaits have evolved in a unique way, and they are like arts.” ¶
She said that she had eaten 2,000 types of parfait in 10 years.

Your meaning is clear here, and the way you wrote it is fine, but it doesn't clearly state that you saw the Finnish woman who lives in Japan on TV. A possible alternative:
"I saw a Finnish woman living in Japan on a TV program who said that,"

Actually, I think parfaits are delicious,; however, I didn’t think it wasthey are unique to Japan.

"However" should follow a semi-colon if it is part of a sentence conjunction. "Parfaits" is a plural noun so we should use "they". I used "are" instead of "were" to match the tense of "I think parfaits are delicious".

I think therey are also in France and so onother places.