Learn Turkish: Araba olsun, bilgisayar olsun, bu markanın her ürünü kaliteli. - Whether it's a car or a computer, every product of this brand is high quality.

Olsun is the third-person imperative of olmak (to be), literally meaning "let it be." When repeated after different nouns like araba olsun, bilgisayar olsun, it creates an inclusive phrase meaning "whether it be a car or a computer." It emphasizes that the statement in the main clause applies equally to all the examples listed.

Could I use gerek ... gerekse ... instead of olsun ... olsun here?

Yes, you could absolutely say gerek araba gerekse bilgisayar. Both structures are used to say "whether X or Y" or "both X and Y." The main difference is tone: olsun ... olsun is very natural in conversational, everyday Turkish, whereas gerek ... gerekse sounds slightly more formal.

Why does ürün have the -ü suffix to become ürünü?

The word ürün (product) takes the third-person possessive suffix -ü because it belongs to bu markanın (this brand's). Together, they form a definite noun compound: markanın ürünü (the brand's product). Slipping the word her (every) in the middle doesn't break this grammatical connection, so the possessive suffix is still required at the end.

Why is there no "to be" suffix like -dir at the end of kaliteli?