How does it work the following swivel chair?

One of those probably releases and tightens the ease of leaning back. Another might adjust arm height. I see you have a few dvds! ;D

RIght. One of them locks the back into place if you prefer that) or allows it to lean.

Another probably allows the arms to be moved wider. A thin person might like them closer together, while a larger person with bigger chest and armspan might like them further apart.

Have you been to the manucturer’s web site and downloaded the manual?

@elbanditoroso: I don’t know who the manufacturer is. Do you have any idea?

Errata corrige: It’s an interstuhl goal.

Could you find the model, please?

I request deletion of this question. I already found the answer.