Master's thesis on The system of punishments and criminal measures in the Criminal Code of 1997, defended with very good distinction from the Faculty of Law and Administration at the University of Wroclaw in 1998, the same year he defended his second thesis about : Rights of creators of literary works in the light of Law on Copyright and Related Rights Act of 4 February 1994, in comparative with other Polish acts of copyright law in the twentieth century at the Institute of Library and Information Science Faculty of Philology at the University of Wroclaw.

In 2000-2004 Mr. Śliwiński completed legal training conducted by the District Chamber of Legal Advisers in Wroclaw and in 2004 was a legal advisor.  In 2006 he was admitted to the bars of the District Bar Council in Wroclaw. His professional activity began in 1996 by working in the litigation department of the greatest, at that time, polish debt collection company. 

In 1999-2004, he was a partner in a law firm, and since 2004 has provided legal support within the framework of his legal adviser law office (until 2006), then within the framework of his law firm. Since 2013 he is a partner in the law firm "RHETOR" Sliwinski & Jasinski professional partnership.