Stiefnu was born in Lija, in 1985. He started his first art lessons under the tuition of Michael Mifsud and later on he continued his studies at the School of Arts and Crafts, Tarġa Gap, Malta, under Herman Baldacchino. He subsequently attended lessons under the tuition of renowned artist Twanny Darmanin at the Art Club 2000. He successfully completed the First Diploma course in Art and Design and subsequently passed the National Diploma in Design Crafts with Distinction, under the guidance of Maltese ceramist George Muscat. He successfully obtained the BTEC Higher National Diploma in 3D Design / Ceramics at MCAST, under the tuition of Maltese artist Alfred Camilleri. In 2006, he completed a one-year course in Fine Arts at the Malta School of Art under the tuition of Alfred Caruana Ruggier. In 2007, Stefan was declared winner of a ceramics competition launched as part of the Medpot Project promoted by the Comune Di Sciacca in Sicily, and received a one-month scholarship in Sciacca. After his experience in Sicily, Stiefnu participated in various collective exhibitions and art festivals, such as Earth Garden Festival and Science in the City. In 2018-2019, Stiefnu participated in an international collective exhibition with the name, Vasi Comunicanti, which toured Santo Stefano Di Camastra, Sciacca and Mazzara Del Vallo in Sicily. In 2019, Stiefnu held his first solo exhibition at the National Labour Centre in Malta, and in 2022 he was chosen to represent Malta at the UNESCO Art Camp that was held in Baku and Shusha, in Azerbaijan.