An adjective for someone who speaks in a way that he can get whatever he wants by using his talking skills

Solution 1:

A successful salesman would need to be

convincing
_ADJECTIVE

Capable of causing someone to believe that something is true or real.

^{From Lexico.}

Such a person has the gift of the gab

The ability to speak to others in a self-assured, persuasive manner.
His gift of the gab made him a wonderful salesman.

^{From Farlex}

and would be able to sell sawdust to a lumber mill:

Someone is an extremely smooth, charming, or persuasive salesperson, such that they could sell something to those who have no need or use for it.

^{Again from Farlex.}