Learn Turkish: Tasarımcı, kumaşları dokunarak seçiyor. - The designer is choosing the fabrics by touching them.

This is the suffix for "by doing" or "while doing" from this lesson. It attaches to the verb root dokun- (to touch). Because the last vowel is 'u', it follows a-type vowel harmony and becomes -arak, meaning "by touching".

The verb dokunmak (to touch) usually takes the dative case. Why does kumaşları have the accusative case here?

Here, kumaşları is the direct object of the main verb seçiyor (choosing), so it takes the accusative case. The designer is choosing the fabrics, and doing so by touching. If the fabrics were the specific object of the touching, you would see the dative: kumaşlara dokunarak.

How is the word tasarımcı (designer) built?

It comes from the noun tasarım (design). The suffix -cı / -ci is a very common ending used to talk about someone's profession or regular activity, turning "design" into "designer".

Why is there a comma right after Tasarımcı?

In Turkish, a comma is frequently used right after the subject of a sentence to clearly separate it from the object and the verb. This makes it instantly clear who is performing the action.