From 1892 until 1896, Mytteis was enrolled at Alexander Pock's academy and after that, until 1900, he studied under Eduard Peithner-Lichtenfels. From 1903, he was active in Villach tätig. From 1903 to 1933, he had an engagement a an art teacher at the Staatsrealschule in Graz. He co-founded the Kärntner Kunstverein (Carinthian artists' assocation); from 1909, he was a mamber of the Genossenschaft bildender Künstler Steiermarks (confederation of artists of Styria) and received numerous awards.