B"H I would like to know a detail of the choreography of Duchan: Is it substantial for Kohen to turn before Blessing Kahal to the right or to the left? Does it matter or it is of no importance?

Thank you for your question. The Shulchan Aruch doesn't mention which side the Cohen should turn first. The Shulchan Aruch just mentions that when saying the words: יברכך, וישמרך, אליך, לך, שלום the Cohen turns to the south and the north (128;45). The reason is to 'spread out' the blessing to tho whole congregation (Mishna berura 128;168). The piskei teshuvot (128;92, comment 449) quotes some poskim that say that the Cohen should first turn to his left which is the congregation's right. However, I saw that Harav Dovid Chai Hacohen holds that the Cohen should first turn to his right and then to his left. (you can see the answer in Hebrew here) Either way is fine. All the best!